Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0008982 protein-N(PI)-phosphohistidine-sugar phosphotransferase activity	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for phosphohistidine-sugar phosphotransferase activity. ManX is the EIIAB component of the mannose PTS and is directly phosphorylated at His-10 (by HPr) and His-175 (EIIA to EIIB transfer), then transfers the phosphoryl group to the sugar substrate (PMID:2681202, PMID:8262947). This is a well-supported core molecular function. The IBA term GO:0008982 uses the generic "carbohydrate" parent; the more specific GO:0022870 (mannose-specific) is also annotated. Both are appropriate at their respective levels. Reason: This IBA annotation correctly captures the core phosphotransferase activity of ManX at an appropriate phylogenetic level. ManX catalyzes PEP-dependent sugar phosphorylation as documented by Erni et al. (PMID:2951378, PMID:2999119) and confirmed by mutagenesis studies (PMID:8262947). The IBA is consistent with the experimentally supported annotations. Supporting Evidence: PMID:2951378 IIIMan (35 kDa) is a hydrophilic protein which is transiently phosphorylated and most likely contains the active site for sugar phosphorylation PMID:2999119 IIIMan can be phosphorylated in a phosphoenolpyruvate-dependent reaction
GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for involvement in PEP-dependent sugar PTS. ManX is an essential component of the mannose PTS (PMID:2951378, PMID:2999119). This is a core biological process. Reason: Core biological process for ManX. The mannose permease mediates sugar transport via the PEP-dependent PTS as shown by multiple studies (PMID:2951378, PMID:2999119). The IBA is phylogenetically sound and experimentally well supported. Supporting Evidence: PMID:2951378 The mannose permease of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation PMID:2999119 The mannose-permease complex of the phosphoenolpyruvate-dependent phosphotranferase system exhibits two apparently unrelated activities
GO:1902495 transmembrane transporter complex	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for localization to a transmembrane transporter complex. ManX associates with the ManY/ManZ integral membrane components to form the ManXYZ transporter complex (PMID:2951378, PMID:2999119). ManX is the peripheral cytoplasmic subunit of this complex. Reason: ManX forms a complex with the transmembrane subunits ManY and ManZ. While ManX itself is soluble/peripheral, it is part of the transmembrane transporter complex. Erni & Zanolari showed IIMan and IIIMan form a complex (PMID:2999119) and the full permease consists of three subunits (PMID:2951378). ComplexPortal CPX-5968 documents the D-mannose-specific enzyme II complex. Supporting Evidence: PMID:2951378 The permease consists of three different subunits, IIIMan, II-PMan, and II-MMan, which are encoded in a single transcriptional unit ptsLPM PMID:2999119 A complex of two proteins, IIMan and IIIMan, was purified to homogeneity from an overproducing strain file:ECOLI/manX/manX-deep-research-falcon.md Multiple sources explicitly place manX with manY and manZ in the manXYZ locus, where manY and manZ encode the membrane permease subunits.
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for cytoplasm localization. This is redundant with the IDA annotation for cytoplasm (PMID:2999119) but is not incorrect. ManX (IIIMan) exists both membrane-associated and free in the cytoplasm (PMID:2999119). Reason: Correct IEA annotation, consistent with experimental evidence. ManX is found both in the cytoplasm and membrane-associated (PMID:2999119). The IDA annotation with the same GO ID provides stronger evidence for the same localization. Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm
GO:0005886 plasma membrane	IEA GO_REF:0000044	ACCEPT	Summary: IEA annotation for plasma membrane localization based on UniProt subcellular location mapping. Consistent with the IDA annotation for the same term (PMID:2999119). Reason: Correct. ManX is a peripheral membrane protein associated with the cell inner membrane (PMID:2999119). Redundant with the IDA-supported annotation but not incorrect. Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm
GO:0008643 carbohydrate transport	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation for carbohydrate transport based on InterPro domain mapping. ManX is involved in transport of mannose, glucose, fructose, and N-acetylglucosamine (PMID:2951378, PMID:2999119). This is a broad parent term; more specific sugar transport terms are also annotated. Reason: Correct but general. ManX participates in the transport of multiple sugars including mannose, glucose, fructose, and N-acetylglucosamine. More specific transport annotations exist (GO:0015761, GO:0098708, GO:1990539, GO:0015764) but this broader IEA term is not wrong. Supporting Evidence: PMID:2951378 The mannose permease of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation
GO:0008982 protein-N(PI)-phosphohistidine-sugar phosphotransferase activity	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation for phosphohistidine-sugar phosphotransferase activity from InterPro domain mapping. Redundant with the IBA annotation for the same GO term. Correct. Reason: Correct IEA annotation consistent with the IBA and experimentally supported function. ManX contains PTS EIIA and EIIB domains that mediate phosphotransfer (PMID:2681202, PMID:8262947).
GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation for PEP-dependent sugar PTS based on InterPro. Redundant with IBA and IDA annotations for the same GO term. Correct. Reason: Correct IEA annotation. ManX is a core component of the PEP-dependent sugar PTS (PMID:2951378, PMID:2999119). Duplicates more authoritative evidence codes for the same term.
GO:0016020 membrane	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation for membrane localization from InterPro. This is a very broad CC term. ManX is a peripheral membrane protein (PMID:2999119). The more specific GO:0005886 (plasma membrane) is also annotated. Reason: Not incorrect but very general. ManX associates with the inner membrane as a peripheral membrane protein (PMID:2999119). More specific terms (GO:0005886) are also present. Acceptable as a broad IEA annotation.
GO:0016773 phosphotransferase activity, alcohol group as acceptor	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation for phosphotransferase activity (alcohol group acceptor) from InterPro. ManX transfers phosphoryl groups to the C6 hydroxyl of mannose (an alcohol group), so this is technically correct. However, the more specific GO:0008982 (protein-N(PI)-phosphohistidine-carbohydrate phosphotransferase activity) and GO:0022870 (mannose-specific PTS transporter activity) are better descriptors. Reason: Correct but very general IEA annotation. ManX phosphorylates sugar substrates at hydroxyl groups. More specific MF terms are already annotated. Acceptable as a broad IEA mapping.
GO:0005515 protein binding	IPI PMID:16606699 Large-scale identification of protein-protein interaction of...	REMOVE	Summary: IPI annotation for protein binding based on large-scale pull-down assay (PMID:16606699). The interacting partner is CytR (P0ACN7) per the GOA WITH column. Per curation guidelines, GO:0005515 (protein binding) is uninformative and should be removed. ManX has well-characterized specific interactions (homodimerization, interaction with HPr) that are captured by more specific terms. Reason: Per curation guidelines, "protein binding" (GO:0005515) is uninformative and does not convey meaningful functional information about ManX. The large-scale pull-down study (PMID:16606699) identifies interactions but the generic "protein binding" term does not add useful annotation. More specific interaction terms like GO:0042803 (protein homodimerization activity) are already annotated. Supporting Evidence: PMID:16606699 A large-scale comprehensive pull-down assay was performed using a His-tagged Escherichia coli ORF clone library
GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system	IDA PMID:2951378 The mannose permease of Escherichia coli consists of three d...	ACCEPT	Summary: IDA annotation for PEP-dependent sugar PTS based on the seminal Erni et al. 1987 paper that characterized the mannose permease as consisting of three subunits mediating sugar transport and phosphorylation via the PTS (PMID:2951378). Reason: Core biological process. Erni et al. 1987 demonstrated that the mannose permease mediates PEP-dependent sugar transport and phosphorylation (PMID:2951378). This is the primary function of ManX. Supporting Evidence: PMID:2951378 The mannose permease of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation
GO:0015761 mannose transmembrane transport	NAS PMID:2951378 The mannose permease of Escherichia coli consists of three d...	ACCEPT	Summary: NAS annotation for mannose transmembrane transport. Erni et al. 1987 explicitly described the mannose permease as mediating mannose transport (PMID:2951378). ManX is the EIIAB component required for mannose transport and phosphorylation. Reason: Mannose transport is the primary named function of the ManXYZ complex. Although ManX alone is not the transmembrane component (ManY/ManZ form the channel), ManX is essential for the transport-coupled phosphorylation. PMID:2951378 states all three subunits are required for sugar transport. Supporting Evidence: PMID:2951378 All three subunits are required for sugar transport and phosphorylation
GO:0015761 mannose transmembrane transport	IDA PMID:5545083 Sugar transport. II. Characterization of constitutive membra...	ACCEPT	Summary: IDA annotation for mannose transmembrane transport based on Kundig & Roseman 1971 (PMID:5545083), which characterized constitutive membrane-bound enzymes II of the E. coli PTS including the mannose-specific system. Reason: This early characterization paper established the mannose-specific PTS enzyme II activity in E. coli membranes. ManX is essential for mannose transport by the ManXYZ complex. Supporting Evidence: PMID:5545083 Sugar transport. II. Characterization of constitutive membrane-bound enzymes II of the Escherichia coli phosphotransferase system
GO:0015764 N-acetylglucosamine transport	EXP PMID:6252281 Amino-sugar transport systems of Escherichia coli K12.	KEEP AS NON CORE	Summary: EXP annotation for N-acetylglucosamine transport. Jones-Mortimer & Kornberg 1980 (PMID:6252281) showed that N-acetylglucosamine enters E. coli by two PTS systems, one of which is the PtsM (ManXYZ) system. This is a secondary transport substrate of the Man-PTS. Reason: N-acetylglucosamine transport via the Man-PTS is experimentally documented (PMID:6252281) but represents a secondary substrate rather than the core mannose/glucose transport function. The Man-PTS has broad substrate specificity. Supporting Evidence: PMID:6252281 N-Acetylglucosamine enters E. coli by two distinct phosphotransferase systems file:ECOLI/manX/manX-deep-research-falcon.md the mannose-family PTS can be promiscuous in substrate handling beyond mannose
GO:0098708 D-glucose import across plasma membrane	IDA PMID:5545083 Sugar transport. II. Characterization of constitutive membra...	KEEP AS NON CORE	Summary: IDA annotation for D-glucose import across plasma membrane. The Man-PTS is known to transport glucose in addition to mannose (PMID:2999119 mentions 2-deoxyglucose transport). Glucose is an important substrate of the Man-PTS. Reason: Glucose transport by the Man-PTS is well established. Erni & Zanolari 1985 showed the mannose permease mediates transport of mannose, 2-deoxyglucose, and other hexoses (PMID:2999119). However, glucose transport is a secondary function; the primary named substrate is mannose. Supporting Evidence: PMID:2999119 It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose, and a number of other hexoses file:ECOLI/manX/manX-deep-research-falcon.md lists substrates associated with the ManXYZ PTS system including mannose, glucose, 2-deoxyglucose, fructose, and amino sugars (including GlcNAc/GlcN)
GO:1990539 fructose import across plasma membrane	EXP PMID:4153999 The role of phosphotransferase-mediated syntheses of fructos...	KEEP AS NON CORE	Summary: EXP annotation for fructose import across plasma membrane. Ferenci & Kornberg 1974 (PMID:4153999) studied PTS-mediated fructose phosphorylation in E. coli. The Man-PTS can transport fructose as a secondary substrate. Reason: Fructose import via the Man-PTS is a secondary transport function. E. coli has a dedicated fructose PTS (FruAB), and fructose transport via the Man-PTS is a minor pathway. This is a legitimate but non-core annotation. Supporting Evidence: PMID:4153999 The role of phosphotransferase-mediated syntheses of fructose 1-phosphate and fructose 6-phosphate in the growth of Escherichia coli on fructose
GO:1990539 fructose import across plasma membrane	EXP PMID:4154035 Genetical analysis of fructose utilization by Escherichia co...	KEEP AS NON CORE	Summary: EXP annotation for fructose import based on Jones-Mortimer & Kornberg 1974 (PMID:4154035), a genetic analysis of fructose utilization showing the Man-PTS can participate in fructose uptake. Reason: Duplicate of the fructose import annotation with a different reference. Fructose transport is a secondary substrate for the Man-PTS. Keeping as non-core. Supporting Evidence: PMID:4154035 Genetical analysis of fructose utilization by Escherichia coli
GO:0005829 cytosol	HDA PMID:16858726 A complexomic study of Escherichia coli using two-dimensiona...	ACCEPT	Summary: HDA annotation for cytosol localization based on complexomic study using 2D BN/SDS-PAGE (PMID:16858726). ManX was identified in the cytosolic fraction. Consistent with its known dual localization (cytoplasm and membrane-associated). Reason: ManX is found in the cytosol as established by multiple approaches. The complexomic study (PMID:16858726) identified ManX in both cytosolic and membrane fractions, consistent with the biochemical evidence (PMID:2999119). Supporting Evidence: PMID:16858726 the cytosolic and membrane protein complexes of Escherichia coli were separated PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm
GO:0005737 cytoplasm	IDA PMID:2999119 The mannose-permease of the bacterial phosphotransferase sys...	ACCEPT	Summary: IDA annotation for cytoplasm localization. Erni & Zanolari 1985 (PMID:2999119) showed that IIIMan (ManX) exists both membrane-associated and free in the cytoplasm. Reason: Well-supported localization. ManX is a soluble/peripheral protein found in the cytoplasm (PMID:2999119). Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm
GO:0005829 cytosol	IDA PMID:2999119 The mannose-permease of the bacterial phosphotransferase sys...	ACCEPT	Summary: IDA annotation for cytosol localization based on Erni & Zanolari 1985 (PMID:2999119). ManX is found free in the cytoplasm/cytosol when not membrane-associated. Reason: Consistent with the biochemical purification showing ManX exists as a soluble cytoplasmic protein (PMID:2999119). Cytosol is a reasonable specific localization for the free form. Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm file:ECOLI/manX/manX-deep-research-falcon.md ManX is annotated as IM, C, consistent with a cytosolic/peripheral phosphotransfer component associated with the inner membrane complex.
GO:0005886 plasma membrane	IDA PMID:2999119 The mannose-permease of the bacterial phosphotransferase sys...	ACCEPT	Summary: IDA annotation for plasma membrane localization. Erni & Zanolari 1985 (PMID:2999119) showed ManX is found membrane-associated. UniProt confirms it is a peripheral membrane protein of the cell inner membrane. Reason: Well-supported localization. ManX associates with the inner (plasma) membrane as a peripheral membrane protein (PMID:2999119). This represents one of its two localizations (cytoplasmic and membrane-associated). Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and free in the cytoplasm
GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system	IDA PMID:2999119 The mannose-permease of the bacterial phosphotransferase sys...	ACCEPT	Summary: IDA annotation for PEP-dependent sugar PTS based on Erni & Zanolari 1985 (PMID:2999119). This paper demonstrated PEP-dependent phosphorylation of IIIMan and reconstituted phosphotransferase activity in vitro. Reason: Core biological process. The paper directly demonstrated PEP-dependent phosphorylation of ManX and reconstituted sugar phosphorylation activity (PMID:2999119). Supporting Evidence: PMID:2999119 IIIMan can be phosphorylated in a phosphoenolpyruvate-dependent reaction
GO:0016301 kinase activity	IDA PMID:2999119 The mannose-permease of the bacterial phosphotransferase sys...	MARK AS OVER ANNOTATED	Summary: IDA annotation for kinase activity. ManX phosphorylates sugar substrates, which is a kinase activity. However, this is a very broad term. The more specific GO:0008982 (protein-N(PI)-phosphohistidine-carbohydrate phosphotransferase activity) and GO:0022870 (mannose-specific PTS transporter activity) better capture this function. Reason: While ManX does have phosphotransferase (kinase-like) activity, GO:0016301 is too broad and does not capture the PTS-specific mechanism. ManX is not a conventional kinase; it transfers phosphoryl groups from phosphohistidine intermediates to sugars as part of the PTS system. The more specific terms GO:0008982 and GO:0022870 are already annotated and better represent this function. GO:0016301 could be misleading. Supporting Evidence: PMID:2999119 IIMan and IIIMan are both required for phosphorylation of 2-deoxyglucose in vitro
GO:0022870 protein-N(PI)-phosphohistidine-mannose phosphotransferase system transporter activity	IDA PMID:5545083 Sugar transport. II. Characterization of constitutive membra...	ACCEPT	Summary: IDA annotation for mannose-specific PTS transporter activity. This is the most specific molecular function term for ManX, capturing both the mannose substrate specificity and the PTS phosphotransferase mechanism. ManX is the EIIAB phosphorylating subunit of the mannose-specific PTS (PMID:2951378, PMID:2999119). Reason: This is the most informative and specific MF term for ManX. It captures the mannose-specific PTS transporter activity that is the core molecular function of the ManXYZ complex. Well supported by multiple studies (PMID:2951378, PMID:2999119, PMID:2681202, PMID:8262947). Supporting Evidence: PMID:2951378 The mannose permease of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation PMID:2999119 It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose, and a number of other hexoses file:ECOLI/manX/manX-deep-research-falcon.md ManX is the mannose-family PTS EIIAB subunit. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components.
GO:0042803 protein homodimerization activity	IDA PMID:2951378 The mannose permease of Escherichia coli consists of three d...	ACCEPT	Summary: IDA annotation for protein homodimerization activity. ManX (IIIMan) forms homodimers as demonstrated by Erni et al. 1987 (PMID:2951378) and confirmed by Erni & Zanolari 1985 (PMID:2999119) and structural studies. UniProt states "Homodimer" with multiple supporting references. Reason: Well-supported molecular function. ManX forms stable homodimers, confirmed by biochemical purification (PMID:2999119), characterization studies (PMID:2951378), and NMR structural studies. Dimerization is functionally relevant as shown by mutagenesis (His-10 and other mutations abolish dimerization; PMID:8262947). Supporting Evidence: PMID:2999119 IIIMan, a 35-kDa protein, exists as a dimer PMID:2951378 IIIMan (35 kDa) is a hydrophilic protein which is transiently phosphorylated
GO:0016020 membrane	HDA PMID:16858726 A complexomic study of Escherichia coli using two-dimensiona...	ACCEPT	Summary: HDA annotation for membrane localization based on the complexomic study (PMID:16858726). ManX was found in both cytosolic and membrane fractions. This is a broad CC term; the more specific GO:0005886 (plasma membrane) is also annotated. Reason: Correct but broad. The complexomic study identified ManX in membrane fractions (PMID:16858726), consistent with its known peripheral membrane association (PMID:2999119). The more specific plasma membrane term is also annotated. Supporting Evidence: PMID:16858726 the cytosolic and membrane protein complexes of Escherichia coli were separated

Core Functions

ManX is the EIIAB phosphorylating subunit of the mannose-specific PTS. It receives a phosphoryl group from HPr at His-10 (EIIA domain), transfers it internally to His-175 (EIIB domain), and then to the sugar substrate during transport by the ManXYZ complex. This is the primary molecular function of ManX (PMID:2681202, PMID:8262947, PMID:2951378).

Molecular Function:

protein-N(PI)-phosphohistidine-mannose phosphotransferase system transporter activity

Directly Involved In:

phosphoenolpyruvate-dependent sugar phosphotransferase system mannose transmembrane transport

Cellular Locations:

cytosol plasma membrane

In Complex:

transmembrane transporter complex

Supporting Evidence:

PMID:2951378
The mannose permease of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation
PMID:2999119
It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose, and a number of other hexoses
file:ECOLI/manX/manX-deep-research-falcon.md
ManX** is the **mannose-family PTS EIIAB subunit**. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a **cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components.

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

file:ECOLI/manX/manX-deep-research-falcon.md

Falcon (Edison Scientific) deep research report: Functional annotation of manX (UniProt P69797) in Escherichia coli K-12

Falcon corroborates ManX as the cytosolic EIIAB phosphotransfer subunit of the mannose-family PTS, distinct from the membrane permease subunits ManY/ManZ.

"ManX** is the **mannose-family PTS EIIAB subunit**. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a **cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components."
Falcon corroborates the manXYZ operon organization, with manY and manZ encoding the membrane permease subunits of the complex.

"Multiple sources explicitly place **manX** with **manY** and **manZ** in the **manXYZ** locus, where manY and manZ encode the membrane permease subunits."
Falcon corroborates the broad/promiscuous substrate range of the Man-PTS beyond mannose, consistent with the secondary glucose, fructose, and N-acetylglucosamine transport annotations marked non-core in this review.

"the mannose-family PTS can be **promiscuous** in substrate handling beyond mannose"
Falcon corroborates a substrate set including mannose, glucose, 2-deoxyglucose, fructose, and amino sugars (GlcNAc/GlcN) for the ManXYZ PTS system.

"lists substrates associated with the ManXYZ PTS system including **mannose, glucose, 2-deoxyglucose, fructose**, and amino sugars (including **GlcNAc/GlcN**)"
Falcon corroborates the dual localization of ManX as a cytosolic/peripheral phosphotransfer component associated with the inner membrane complex.

"ManX is annotated as **IM, C**, consistent with a **cytosolic/peripheral phosphotransfer component associated with the inner membrane complex**."

PMID:16606699

Large-scale identification of protein-protein interaction of Escherichia coli K-12.

Large-scale pull-down assay using His-tagged E. coli ORF clone library identified protein-protein interactions for 2667 bait proteins. ManX interaction with CytR was identified. This is a high-throughput study and individual interactions should be treated with caution.

PMID:16858726

A complexomic study of Escherichia coli using two-dimensional blue native/SDS polyacrylamide gel electrophoresis.

Complexomic study separated cytosolic and membrane protein complexes of E. coli. ManX was identified in both cytosolic and membrane fractions, consistent with its known dual localization.

PMID:2951378

The mannose permease of Escherichia coli consists of three different proteins. Amino acid sequence and function in sugar transport, sugar phosphorylation, and penetration of phage lambda DNA.

Demonstrated that the mannose permease consists of three subunits (IIIMan/ManX, II-PMan/ManY, II-MMan/ManZ) encoded in a single transcriptional unit. All three are required for sugar transport and phosphorylation. ManX (IIIMan, 35 kDa) is a hydrophilic protein that is transiently phosphorylated and contains the active site for sugar phosphorylation. The permease also functions as a receptor for bacterial chemotaxis and is required for bacteriophage lambda DNA penetration (II-PMan and II-MMan are sufficient for lambda DNA penetration).

PMID:2999119

The mannose-permease of the bacterial phosphotransferase system. Gene cloning and purification of the enzyme IIMan/IIIMan complex of Escherichia coli.

Cloned ptsM and ptsL genes and purified IIMan/IIIMan complex. IIIMan (ManX, 35 kDa) exists as a dimer, found both membrane-associated and free in the cytoplasm. IIIMan can be phosphorylated in a PEP-dependent reaction. Both IIMan and IIIMan are required for phosphorylation of 2-deoxyglucose in vitro.

PMID:2681202

Mannose permease of Escherichia coli. Domain structure and function of the phosphorylating subunit.

Demonstrated that ManX (EIIAB) has two phosphorylation sites: His-10 in the EIIA domain (phosphorylated by HPr) and His-175 in the EIIB domain (phosphorylated by EIIA). The protein consists of distinct EIIA and EIIB domains connected by a hinge region.

PMID:8262947

The mannose transporter of Escherichia coli. Structure and function of the IIABMan subunit.

Mutagenesis studies confirmed His-10 and His-175 as active site residues. H10C and H175C mutations abolish phosphotransferase activity. H10C also prevents dimerization. H86N mutation abolishes activity, indicating His-86 involvement in phosphoryl transfer between the two domains. EC 2.7.1.191 catalytic activity confirmed.

PMID:4153999

The role of phosphotransferase-mediated syntheses of fructose 1-phosphate and fructose 6-phosphate in the growth of Escherichia coli on fructose.

Studied PTS-mediated fructose phosphorylation pathways in E. coli growth on fructose. The Man-PTS can participate in fructose uptake as a secondary substrate.

PMID:4154035

Genetical analysis of fructose utilization by Escherichia coli.

Genetic analysis of fructose utilization pathways showing multiple PTS systems can transport fructose in E. coli.

PMID:5545083

Sugar transport. II. Characterization of constitutive membrane-bound enzymes II of the Escherichia coli phosphotransferase system.

Early characterization of constitutive membrane-bound PTS enzymes II in E. coli, including the mannose-specific system.

PMID:6252281

Amino-sugar transport systems of Escherichia coli K12.

Demonstrated that N-acetylglucosamine enters E. coli by two PTS systems, one being the PtsM (Man-PTS) system. Glucosamine, mannose and 2-deoxyglucose also enter via PtsM.

PMID:4604906

Phosphotransferase-system enzymes as chemoreceptors for certain sugars in Escherichia coli chemotaxis.

Demonstrated that PTS enzymes, including the mannose PTS, function as chemoreceptors for sugar chemotaxis in E. coli.

PMID:353494

E. coli K-12 pel mutants, which block phage lambda DNA injection, coincide with ptsM, which determines a component of a sugar transport system.

Showed that pel mutants blocking phage lambda DNA injection map to ptsM, establishing the Man-PTS as the receptor for lambda DNA penetration.

Deep Research

Falcon

(manX-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 14 citations 2 artifacts 2026-06-01T04:08:14.442039

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000006 Figure 1A provides a schematic of the E. coli phosphotransferase system (PTS). This panel specifically illustrates the alternative (image/png)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research report: Functional annotation of manX (UniProt P69797) in Escherichia coli K-12

0) Identity verification (critical disambiguation)

The literature and reviews retrieved here consistently describe manX in E. coli as the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) mannose-family EIIAB component, found in the manXYZ locus with manY and manZ encoding the membrane components. This matches the user-supplied UniProt target description for accession P69797 (mannose-specific PTS EIIAB component, “EIIAB-Man/EIII-Man”, part of manXYZ). In a recent E. coli glucose-transport review, manX is explicitly labeled “mannose-specific PTS system EIIAB”, while manYZ are labeled “EIICD” components, consistent with the canonical mannose-family PTS architecture. (carreonrodriguez2023glucosetransportin pages 2-3)

1) Key concepts and current understanding

1.1 The PTS and mannose-family Enzyme II systems

The bacterial PTS is a group translocation system in which transport is coupled to phosphorylation. A phosphate derived from PEP is transferred through a cascade (classically EI → HPr → EII components) and ultimately to the incoming carbohydrate, thereby importing the sugar in a phosphorylated form and integrating uptake with central carbon metabolism and regulation. A 2024 Cra review summarizes this mechanism as a “phosphorylation cascade” used to transport carbohydrates. (huang2024insightsintothe pages 6-8)

Within E. coli, mannose-family PTS transporters are commonly organized as:
- a cytosolic phosphotransfer module (EIIA/EIIB; sometimes fused), and
- an inner-membrane transport module (EIIC and often EIID in mannose-family systems).
A 2023 review’s curated transporter table places ManX as “EIIAB” and ManYZ as “EIICD”, indicating a split between a cytosolic EIIAB and membrane EIICD components. (carreonrodriguez2023glucosetransportin pages 2-3)

1.2 What ManX is (definition)

ManX is the mannose-family PTS EIIAB subunit. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a cytosolic component (IM, C), consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components. (carreonrodriguez2023glucosetransportin pages 2-3)

Operon/context: Multiple sources explicitly place manX with manY and manZ in the manXYZ locus, where manY and manZ encode the membrane permease subunits. (huang2024insightsintothe pages 6-8, carreonrodriguez2023glucosetransportin pages 2-3, mukherjee2024plasticityofgrowth pages 6-7)

1.3 Reaction catalyzed and mechanistic role

The retrieved sources provide strong evidence for ManX’s role in phosphoryl-transfer-coupled carbohydrate uptake as part of the PTS cascade, including explicit pathway schematics showing a mannose-family EIIAB module (“P~EIIABMan”) participating in PTS-mediated phosphorylation and import routes. (carreonrodriguez2023glucosetransportin pages 3-4, carreonrodriguez2023glucosetransportin media f2cbe0f1)

However, the specific EC number (EC 2.7.1.191) and the exact enzyme name variant “EIII-Man” were not explicitly stated in the retrieved full-text excerpts, so those details should be treated as UniProt-provided annotation for P69797 rather than independently re-validated here.

2) Substrate specificity and physiological role

2.1 Substrate range

Authoritative transport summaries list the manXYZ system under mannose transport. (carreonrodriguez2023glucosetransportin pages 2-3)

Additional recent E. coli-focused evidence indicates the mannose-family PTS can be promiscuous in substrate handling beyond mannose. A 2024 E. coli metabolic-oligosaccharide engineering context describes ManXYZ as a “promiscuous mannose PTS transporter” with activity toward mannose, GlcNAc, GlcN, and other hexoses, and indicates PTS import yields the corresponding sugar-6-phosphate, which can be a critical constraint for downstream metabolic engineering. (tsengwest2024exploringnahkmediatedmetabolic pages 46-49)

A separate excerpted table (same 2024 source) lists substrates associated with the ManXYZ PTS system including mannose, glucose, 2-deoxyglucose, fructose, and amino sugars (including GlcNAc/GlcN), supporting practical cross-specificity in curated/engineering contexts. (tsengwest2024exploringnahkmediatedmetabolic pages 36-39)

2.2 Biological processes and pathway context

ManX functions in carbohydrate uptake and phosphorylation within the PTS framework and is embedded in broader carbon control networks. The Cra review places manX/manY/manZ among PTS-linked components relevant to carbon utilization regulation, reinforcing that ManX is not just a transporter component but also part of global regulatory wiring around carbon flux and catabolite regulation. (huang2024insightsintothe pages 6-8)

3) Cellular localization and complex organization

Curated localization indicates:
- ManX (EIIAB): “IM, C” (inner membrane–associated; cytosolic), consistent with a cytosolic enzyme subunit functionally coupled to a membrane permease complex. (carreonrodriguez2023glucosetransportin pages 2-3)
- ManY/ManZ (EIICD/EIIC+EIID): inner-membrane components forming the translocation pathway. (carreonrodriguez2023glucosetransportin pages 2-3)

A 2024 source explicitly separates ManX (IIAB) from ManY (IIC) and ManZ (IID), consistent with mannose-family PTS architecture. (tsengwest2024exploringnahkmediatedmetabolic pages 36-39)

4) Recent developments (prioritizing 2023–2024)

4.1 2023: Transport engineering perspective (systems-level view)

A 2023 review of E. coli glucose transport emphasizes that multiple transporters can contribute to glucose entry and phosphorylation, including mannose-family components, highlighting “cross-taking interactions” and non-specific contributions of alternative systems. A pathway schematic includes the mannose-family phosphotransfer module labeled “P~EIIABMan.” (Publication date: 2023-06; URL: https://doi.org/10.3390/microorganisms11061588) (carreonrodriguez2023glucosetransportin pages 3-4, carreonrodriguez2023glucosetransportin media f2cbe0f1)

4.2 2024: Regulatory rewiring can transform mannose ‘nutrient quality’

A 2024 study on growth laws demonstrated that mannose performance in E. coli is strongly influenced by regulatory/proteome allocation decisions. The authors engineered the manXYZ locus by:
- swapping in the glucose PTS promoter PptsG upstream of manX,
- deleting the regulator mlc, and
- placing manA (mannose-6-phosphate isomerase) under a strong promoter.
They report that the engineered strain grows on mannose as fast as wild-type grows on glucose (statistical comparisons show WT glucose vs WT mannose: P < 0.0001; WT mannose vs engineered mannose: P < 0.0001; WT glucose vs engineered mannose: ns). This directly supports a modern view that the manXYZ/ManX module’s physiological impact is highly tunable by expression/regulation, not only by intrinsic transporter/enzyme kinetics. (Publication date: 2024-01; URL: https://doi.org/10.1371/journal.pcbi.1011735) (mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10, mukherjee2024plasticityofgrowth pages 6-7)

4.3 2024: PTS-linked global regulation (Cra)

A 2024 review on the transcription factor Cra contextualizes PTS systems (including manX/manY/manZ) within global carbon control and regulatory cascades, emphasizing that PTS components participate in carbohydrate transport via phosphorylation cascades and are part of networks shaping carbon utilization strategies. (Publication date: 2024-11; URL: https://doi.org/10.1128/aem.01228-24) (huang2024insightsintothe pages 6-8)

5) Current applications and real-world implementations

5.1 Metabolic engineering and transport engineering

The 2023 glucose-transport review explicitly frames E. coli sugar transport systems (including mannose-family PTS components) as levers for transport engineering to improve growth and production phenotypes, i.e., rebalancing transporter usage and regulatory circuits to optimize flux toward desired products. (carreonrodriguez2023glucosetransportin pages 3-4)

The 2024 growth-law work is a concrete demonstration of this principle: by rewiring manXYZ/manX expression (plus manA) the authors convert mannose from a poor to a high-performance substrate, which is directly relevant to industrial or lab-scale strain optimization when mannose-rich feedstocks are used. (mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)

5.2 Glyco-/amino-sugar and analog uptake constraints (engineering context)

In metabolic oligosaccharide engineering contexts, ManXYZ is discussed as a relevant entry route for amino sugars/analogs, with the key practical constraint that PTS import produces sugar-6-phosphates (e.g., phosphorylated analogs), shaping downstream pathway design needs (e.g., dephosphorylation steps or alternative uptake strategies). (tsengwest2024exploringnahkmediatedmetabolic pages 46-49)

6) Expert opinions and analysis (authoritative sources)

The 2023 review synthesizes a consensus view that E. coli carbohydrate uptake is modular and includes redundancy/overlap among transporters, with mannose-family PTS components contributing to broader carbohydrate uptake possibilities. (carreonrodriguez2023glucosetransportin pages 3-4)
The 2024 growth-law study provides an explicit interpretation that mannose is “not an inherently ‘poor’ substrate” and that growth limitations are largely due to regulatory allocation of proteomic resources, supported by promoter rewiring experiments on manXYZ/manX. (mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)
The 2024 Cra review provides a regulatory systems interpretation—placing manX within global carbon management networks—supporting the view that ManX’s physiological role cannot be separated from regulatory state. (huang2024insightsintothe pages 6-8)

7) Relevant statistics and recent quantitative data

Statistical evidence of engineered phenotype (2024): Comparisons reported include P < 0.0001 for (i) WT glucose vs WT mannose growth and (ii) WT mannose vs engineered mannose growth; and non-significant difference between WT glucose vs engineered mannose growth, consistent with engineered mannose growth matching WT glucose growth. (mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)
Experimental parameters (2024): Growth assays were performed in minimal medium with 20 mM glucose or 20 mM mannose at 37°C, OD600-based growth-rate fitting, and cAMP supplementation/rescue conditions were described (including cAMP addition for rescue tests). These details help interpret the comparability of growth phenotypes and establish methodological rigor. (mukherjee2024plasticityofgrowth pages 6-7)

8) Visual evidence (figure support)

A pathway schematic (Figure 1A) from the 2023 review explicitly shows a mannose-family PTS phosphotransfer component labeled “P~EIIABMan” within the broader PTS network for carbohydrate import/phosphorylation. This supports ManX’s conceptual role as the mannose-family EIIAB phosphotransfer module embedded in the PTS cascade. (carreonrodriguez2023glucosetransportin media f2cbe0f1)

9) Summary table (evidence-backed functional annotation)

Aspect	Key points	Supporting sources
identity/operon	• Verified target matches E. coli K-12 manX, annotated as the mannose-specific PTS EIIAB component. • Retrieved sources place manX with manY/manZ in the manXYZ mannose PTS locus. • Alternative naming in retrieved texts includes EIIAB-Man; broader PTS schematics show the mannose-family EIIAB module.	(huang2024insightsintothe pages 6-8, carreonrodriguez2023glucosetransportin pages 2-3, mukherjee2024plasticityofgrowth pages 6-7)
domains/subunits	• ManX is the cytosolic EIIAB phosphotransfer subunit of the mannose-family PTS. • ManY/ManZ correspond to the membrane EIIC/EIID (or EIICD) transport subunits. • This supports a split system with soluble phosphotransfer and membrane translocation components.	(tsengwest2024exploringnahkmediatedmetabolic pages 36-39, huang2024insightsintothe pages 6-8, carreonrodriguez2023glucosetransportin pages 2-3)
reaction/mechanism	• ManX functions in the PEP-dependent phosphotransferase system (PTS), where phosphate flows PEP → EI → HPr → EII components → incoming sugar. • Retrieved texts support phosphoryl-transfer-coupled uptake, but do not directly provide the EC assignment. • EC 2.7.1.191 is reported in the UniProt target description; not directly evidenced in retrieved texts.	(huang2024insightsintothe pages 6-8, carreonrodriguez2023glucosetransportin pages 3-4, carreonrodriguez2023glucosetransportin media f2cbe0f1)
substrates	• Core assignment is mannose-specific transport. • Retrieved evidence also indicates cross-specificity/promiscuity toward glucose, GlcNAc, GlcN, 2-deoxyglucose, fructose, and other hexoses in some assay/database contexts. • Thus, ManX belongs to a mannose-family PTS with broader hexose/amino-sugar handling than mannose alone.	(tsengwest2024exploringnahkmediatedmetabolic pages 36-39, tsengwest2024exploringnahkmediatedmetabolic pages 46-49, carreonrodriguez2023glucosetransportin pages 2-3, carreonrodriguez2023glucosetransportin pages 3-4)
localization	• ManX is annotated as IM, C, consistent with a cytosolic/peripheral phosphotransfer component associated with the inner membrane complex. • ManY/ManZ are inner-membrane components that provide the translocation pathway. • System architecture therefore places catalysis at the cytosolic side of an inner-membrane transporter complex.	(tsengwest2024exploringnahkmediatedmetabolic pages 36-39, carreonrodriguez2023glucosetransportin pages 2-3)
regulation/physiology	• A 2024 Cra review places manX/manY/manZ within broader carbon-control circuitry of the PTS. • A 2024 growth-law study engineered the manXYZ locus by swapping the PptsG promoter upstream of manX, deleting mlc, and strengthening manA expression. • Engineered cells grew on mannose as fast as WT on glucose; WT glucose vs WT mannose and WT mannose vs engineered mannose were both P < 0.0001, while WT glucose vs engineered mannose was ns, indicating regulation/expression—not intrinsic substrate chemistry alone—limits mannose performance.	(huang2024insightsintothe pages 6-8, mukherjee2024plasticityofgrowth pages 6-7, mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)
applications/engineering	• Transport engineering in E. coli exploits mannose-family PTS components as alternative or enhanced sugar-uptake routes. • Rewiring manXYZ/manX expression can convert mannose from a relatively poor to a high-performance substrate for growth. • Recent metabolic-engineering contexts also mention manXYZ deletion or exploitation when redirecting carbohydrate flux or controlling uptake of amino sugars/analogs.	(carreonrodriguez2023glucosetransportin pages 3-4, mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)

Table: This table summarizes the evidence-backed functional annotation of E. coli K-12 ManX (UniProt P69797), including identity, mechanism, substrates, localization, regulation, and engineering relevance. It uses only the retrieved context sources and flags where UniProt information was not directly evidenced in those texts.

10) Evidence gaps and limits of this retrieval

The UniProt-provided details EC 2.7.1.191 and alternative name EIII-Man for P69797 were not directly reproduced in the retrieved excerpts; the texts here support PTS phosphotransfer function and architecture but do not restate the EC designation.
Foundational primary literature linked to older PubMed IDs listed in UniProt could not be retrieved in the current tool runs; therefore, classic biochemical details (e.g., specific phosphorylated residues, kinetic constants of purified ManX/EIIAB-Man) are not included from primary sources in this report.

Key references (with dates and URLs)

Carreón-Rodríguez OE et al. “Glucose Transport in Escherichia coli: From Basics to Transport Engineering.” Microorganisms (2023-06). https://doi.org/10.3390/microorganisms11061588 (carreonrodriguez2023glucosetransportin pages 2-3, carreonrodriguez2023glucosetransportin pages 3-4, carreonrodriguez2023glucosetransportin media f2cbe0f1)
Huang Y et al. “Insights into the regulatory mechanisms and application prospects of the transcription factor Cra.” Applied and Environmental Microbiology (2024-11). https://doi.org/10.1128/aem.01228-24 (huang2024insightsintothe pages 6-8)
Mukherjee A et al. “Plasticity of growth laws tunes resource allocation strategies in bacteria.” PLOS Computational Biology (2024-01). https://doi.org/10.1371/journal.pcbi.1011735 (mukherjee2024plasticityofgrowth pages 6-7, mukherjee2024plasticityofgrowth pages 10-11, mukherjee2024plasticityofgrowth pages 9-10)
Tseng-West M. “Exploring NahK-mediated Metabolic Oligosaccharide Engineering…” (2024; venue unclear in retrieved text). (tsengwest2024exploringnahkmediatedmetabolic pages 36-39, tsengwest2024exploringnahkmediatedmetabolic pages 46-49)

References

(carreonrodriguez2023glucosetransportin pages 2-3): Ofelia E. Carreón-Rodríguez, Guillermo Gosset, Adelfo Escalante, and Francisco Bolívar. Glucose transport in escherichia coli: from basics to transport engineering. Microorganisms, 11:1588, Jun 2023. URL: https://doi.org/10.3390/microorganisms11061588, doi:10.3390/microorganisms11061588. This article has 76 citations.
(huang2024insightsintothe pages 6-8): Ying Huang, Kai-Zhi Jia, Wei Zhao, and Li-Wen Zhu. Insights into the regulatory mechanisms and application prospects of the transcription factor cra. Applied and Environmental Microbiology, Nov 2024. URL: https://doi.org/10.1128/aem.01228-24, doi:10.1128/aem.01228-24. This article has 1 citations and is from a peer-reviewed journal.
(mukherjee2024plasticityofgrowth pages 6-7): Avik Mukherjee, Yu-Fang Chang, Yanqing Huang, Nina Catherine Benites, Leander Ammar, Jade Ealy, Mark Polk, and Markus Basan. Plasticity of growth laws tunes resource allocation strategies in bacteria. PLOS Computational Biology, 20:e1011735, Jan 2024. URL: https://doi.org/10.1371/journal.pcbi.1011735, doi:10.1371/journal.pcbi.1011735. This article has 10 citations and is from a highest quality peer-reviewed journal.
(carreonrodriguez2023glucosetransportin pages 3-4): Ofelia E. Carreón-Rodríguez, Guillermo Gosset, Adelfo Escalante, and Francisco Bolívar. Glucose transport in escherichia coli: from basics to transport engineering. Microorganisms, 11:1588, Jun 2023. URL: https://doi.org/10.3390/microorganisms11061588, doi:10.3390/microorganisms11061588. This article has 76 citations.
(carreonrodriguez2023glucosetransportin media f2cbe0f1): Ofelia E. Carreón-Rodríguez, Guillermo Gosset, Adelfo Escalante, and Francisco Bolívar. Glucose transport in escherichia coli: from basics to transport engineering. Microorganisms, 11:1588, Jun 2023. URL: https://doi.org/10.3390/microorganisms11061588, doi:10.3390/microorganisms11061588. This article has 76 citations.
(tsengwest2024exploringnahkmediatedmetabolic pages 46-49): M Tseng-West. Exploring nahk-mediated metabolic oligosaccharide engineering with n-azidoacetylglucosamine derivatives in escherichia coli. Unknown journal, 2024.
(tsengwest2024exploringnahkmediatedmetabolic pages 36-39): M Tseng-West. Exploring nahk-mediated metabolic oligosaccharide engineering with n-azidoacetylglucosamine derivatives in escherichia coli. Unknown journal, 2024.
(mukherjee2024plasticityofgrowth pages 10-11): Avik Mukherjee, Yu-Fang Chang, Yanqing Huang, Nina Catherine Benites, Leander Ammar, Jade Ealy, Mark Polk, and Markus Basan. Plasticity of growth laws tunes resource allocation strategies in bacteria. PLOS Computational Biology, 20:e1011735, Jan 2024. URL: https://doi.org/10.1371/journal.pcbi.1011735, doi:10.1371/journal.pcbi.1011735. This article has 10 citations and is from a highest quality peer-reviewed journal.
(mukherjee2024plasticityofgrowth pages 9-10): Avik Mukherjee, Yu-Fang Chang, Yanqing Huang, Nina Catherine Benites, Leander Ammar, Jade Ealy, Mark Polk, and Markus Basan. Plasticity of growth laws tunes resource allocation strategies in bacteria. PLOS Computational Biology, 20:e1011735, Jan 2024. URL: https://doi.org/10.1371/journal.pcbi.1011735, doi:10.1371/journal.pcbi.1011735. This article has 10 citations and is from a highest quality peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Citations

carreonrodriguez2023glucosetransportin pages 2-3
huang2024insightsintothe pages 6-8
tsengwest2024exploringnahkmediatedmetabolic pages 46-49
tsengwest2024exploringnahkmediatedmetabolic pages 36-39
carreonrodriguez2023glucosetransportin pages 3-4
mukherjee2024plasticityofgrowth pages 6-7
mukherjee2024plasticityofgrowth pages 10-11
mukherjee2024plasticityofgrowth pages 9-10
https://doi.org/10.3390/microorganisms11061588
https://doi.org/10.1371/journal.pcbi.1011735
https://doi.org/10.1128/aem.01228-24
https://doi.org/10.3390/microorganisms11061588,
https://doi.org/10.1128/aem.01228-24,
https://doi.org/10.1371/journal.pcbi.1011735,

📚 Additional Documentation

Notes

(manX-notes.md)

ManX (EIIAB-Man) - Research Notes

Summary

ManX (P69797) is the cytoplasmic EIIAB phosphorylating subunit of the mannose-specific PTS in E. coli K12. It is encoded by the manXYZ operon (b1817).

Key findings

Domain structure and phosphorylation

ManX is a bifunctional protein with N-terminal EIIA domain (residues 2-124) and C-terminal EIIB domain (residues 157-320), connected by a flexible hinge PMID:2681202
EIIA domain is phosphorylated by HPr at His-10 (tele-phosphohistidine) [PMID:2681202, PMID:8262947]
EIIB domain is phosphorylated at His-175 (pros-phosphohistidine) by EIIA [PMID:2681202, PMID:8262947]
His-86 is involved in phosphoryl transfer between domains PMID:8262947

Dimerization

ManX forms stable homodimers PMID:2999119
H10C mutation abolishes dimerization PMID:8262947
NMR structure of IIAMan-HPr complex (PDB: 1VRC) shows 48 kDa complex PMID:15788390

Localization

Dual localization: found both membrane-associated and free in cytoplasm PMID:2999119
Peripheral membrane protein associated with inner membrane PMID:16079137

Substrate specificity

Primary substrates: mannose, glucose (2-deoxyglucose)
Secondary substrates: fructose [PMID:4153999, PMID:4154035], N-acetylglucosamine PMID:6252281

Regulation

manXYZ operon positively regulated by cAMP-CRP complex PMID:9484892
Negatively regulated by Mlc transcriptional repressor PMID:9484892
Weakly repressed by NagC PMID:11361067

Additional functions

ManXYZ complex serves as chemoreceptor for sugar chemotaxis PMID:4604906
ManXYZ required for phage lambda DNA injection, but ManY/ManZ alone sufficient [PMID:353494, PMID:2951378]

Review decisions

Removed GO:0005515 (protein binding) - uninformative per curation guidelines
Marked GO:0016301 (kinase activity) as over-annotated - too broad for PTS phosphotransferase
Core MF: GO:0022870 (mannose PTS transporter activity)
Secondary substrates (fructose, GlcNAc, glucose) kept as non-core

📄 View Raw YAML

id: P69797
gene_symbol: manX
product_type: PROTEIN
status: IN_PROGRESS
taxon:
  id: NCBITaxon:83333
  label: Escherichia coli (strain K12)
description: >-
  ManX (also known as EIIAB-Man or EIII-Man) is the cytoplasmic phosphorylating subunit of the
  mannose-specific phosphoenolpyruvate-dependent phosphotransferase system (Man-PTS) in E. coli K12.
  It is a bifunctional protein containing two PTS domains: an N-terminal EIIA domain (phosphorylated
  by HPr at His-10) and a C-terminal EIIB domain (phosphorylated at His-175), connected by a
  flexible hinge region. ManX forms homodimers and functions together with the integral membrane
  subunits ManY (EIIC) and ManZ (EIID) to transport and phosphorylate mannose, glucose,
  2-deoxyglucose, fructose, and N-acetylglucosamine via PEP-dependent phosphorylation. ManX exists
  both free in the cytoplasm and associated with the inner membrane. The ManXYZ complex also serves
  as a receptor for bacteriophage lambda DNA injection and as a chemoreceptor for sugars in
  bacterial chemotaxis.
existing_annotations:
- term:
    id: GO:0008982
    label: protein-N(PI)-phosphohistidine-sugar phosphotransferase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for phosphohistidine-sugar phosphotransferase activity. ManX is the EIIAB
      component of the mannose PTS and is directly phosphorylated at His-10 (by HPr) and His-175
      (EIIA to EIIB transfer), then transfers the phosphoryl group to the sugar substrate
      (PMID:2681202, PMID:8262947). This is a well-supported core molecular function. The IBA term
      GO:0008982 uses the generic "carbohydrate" parent; the more specific GO:0022870
      (mannose-specific) is also annotated. Both are appropriate at their respective levels.
    action: ACCEPT
    reason: >-
      This IBA annotation correctly captures the core phosphotransferase activity of ManX at an
      appropriate phylogenetic level. ManX catalyzes PEP-dependent sugar phosphorylation as
      documented by Erni et al. (PMID:2951378, PMID:2999119) and confirmed by mutagenesis studies
      (PMID:8262947). The IBA is consistent with the experimentally supported annotations.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          IIIMan (35 kDa) is a hydrophilic protein which is transiently phosphorylated and most
          likely contains the active site for sugar phosphorylation
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan can be phosphorylated in a phosphoenolpyruvate-dependent reaction

- term:
    id: GO:0009401
    label: phosphoenolpyruvate-dependent sugar phosphotransferase system
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for involvement in PEP-dependent sugar PTS. ManX is an essential component
      of the mannose PTS (PMID:2951378, PMID:2999119). This is a core biological process.
    action: ACCEPT
    reason: >-
      Core biological process for ManX. The mannose permease mediates sugar transport via the
      PEP-dependent PTS as shown by multiple studies (PMID:2951378, PMID:2999119). The IBA is
      phylogenetically sound and experimentally well supported.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The mannose permease of the bacterial phosphotransferase system mediates sugar transport
          across the cytoplasmic membrane concomitant with sugar phosphorylation
      - reference_id: PMID:2999119
        supporting_text: >-
          The mannose-permease complex of the phosphoenolpyruvate-dependent phosphotranferase
          system exhibits two apparently unrelated activities

- term:
    id: GO:1902495
    label: transmembrane transporter complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for localization to a transmembrane transporter complex. ManX associates with
      the ManY/ManZ integral membrane components to form the ManXYZ transporter complex
      (PMID:2951378, PMID:2999119). ManX is the peripheral cytoplasmic subunit of this complex.
    action: ACCEPT
    reason: >-
      ManX forms a complex with the transmembrane subunits ManY and ManZ. While ManX itself is
      soluble/peripheral, it is part of the transmembrane transporter complex. Erni & Zanolari
      showed IIMan and IIIMan form a complex (PMID:2999119) and the full permease consists of
      three subunits (PMID:2951378). ComplexPortal CPX-5968 documents the D-mannose-specific
      enzyme II complex.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The permease consists of three different subunits, IIIMan, II-PMan, and II-MMan, which
          are encoded in a single transcriptional unit ptsLPM
      - reference_id: PMID:2999119
        supporting_text: >-
          A complex of two proteins, IIMan and IIIMan, was purified to homogeneity from an
          overproducing strain
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          Multiple sources explicitly place **manX** with **manY** and **manZ** in the **manXYZ** locus, where manY and manZ encode the membrane permease subunits.

- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >-
      IEA annotation for cytoplasm localization. This is redundant with the IDA annotation for
      cytoplasm (PMID:2999119) but is not incorrect. ManX (IIIMan) exists both membrane-associated
      and free in the cytoplasm (PMID:2999119).
    action: ACCEPT
    reason: >-
      Correct IEA annotation, consistent with experimental evidence. ManX is found both in the
      cytoplasm and membrane-associated (PMID:2999119). The IDA annotation with the same GO ID
      provides stronger evidence for the same localization.
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm

- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >-
      IEA annotation for plasma membrane localization based on UniProt subcellular location mapping.
      Consistent with the IDA annotation for the same term (PMID:2999119).
    action: ACCEPT
    reason: >-
      Correct. ManX is a peripheral membrane protein associated with the cell inner membrane
      (PMID:2999119). Redundant with the IDA-supported annotation but not incorrect.
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm

- term:
    id: GO:0008643
    label: carbohydrate transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      IEA annotation for carbohydrate transport based on InterPro domain mapping. ManX is involved
      in transport of mannose, glucose, fructose, and N-acetylglucosamine (PMID:2951378,
      PMID:2999119). This is a broad parent term; more specific sugar transport terms are also
      annotated.
    action: ACCEPT
    reason: >-
      Correct but general. ManX participates in the transport of multiple sugars including mannose,
      glucose, fructose, and N-acetylglucosamine. More specific transport annotations exist
      (GO:0015761, GO:0098708, GO:1990539, GO:0015764) but this broader IEA term is not wrong.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The mannose permease of the bacterial phosphotransferase system mediates sugar transport
          across the cytoplasmic membrane concomitant with sugar phosphorylation

- term:
    id: GO:0008982
    label: protein-N(PI)-phosphohistidine-sugar phosphotransferase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      IEA annotation for phosphohistidine-sugar phosphotransferase activity from InterPro domain
      mapping. Redundant with the IBA annotation for the same GO term. Correct.
    action: ACCEPT
    reason: >-
      Correct IEA annotation consistent with the IBA and experimentally supported function.
      ManX contains PTS EIIA and EIIB domains that mediate phosphotransfer (PMID:2681202,
      PMID:8262947).

- term:
    id: GO:0009401
    label: phosphoenolpyruvate-dependent sugar phosphotransferase system
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      IEA annotation for PEP-dependent sugar PTS based on InterPro. Redundant with IBA and IDA
      annotations for the same GO term. Correct.
    action: ACCEPT
    reason: >-
      Correct IEA annotation. ManX is a core component of the PEP-dependent sugar PTS
      (PMID:2951378, PMID:2999119). Duplicates more authoritative evidence codes for the same
      term.

- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      IEA annotation for membrane localization from InterPro. This is a very broad CC term.
      ManX is a peripheral membrane protein (PMID:2999119). The more specific GO:0005886
      (plasma membrane) is also annotated.
    action: ACCEPT
    reason: >-
      Not incorrect but very general. ManX associates with the inner membrane as a peripheral
      membrane protein (PMID:2999119). More specific terms (GO:0005886) are also present.
      Acceptable as a broad IEA annotation.

- term:
    id: GO:0016773
    label: phosphotransferase activity, alcohol group as acceptor
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      IEA annotation for phosphotransferase activity (alcohol group acceptor) from InterPro.
      ManX transfers phosphoryl groups to the C6 hydroxyl of mannose (an alcohol group), so
      this is technically correct. However, the more specific GO:0008982
      (protein-N(PI)-phosphohistidine-carbohydrate phosphotransferase activity) and GO:0022870
      (mannose-specific PTS transporter activity) are better descriptors.
    action: ACCEPT
    reason: >-
      Correct but very general IEA annotation. ManX phosphorylates sugar substrates at hydroxyl
      groups. More specific MF terms are already annotated. Acceptable as a broad IEA mapping.

- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16606699
  review:
    summary: >-
      IPI annotation for protein binding based on large-scale pull-down assay (PMID:16606699).
      The interacting partner is CytR (P0ACN7) per the GOA WITH column. Per curation guidelines,
      GO:0005515 (protein binding) is uninformative and should be removed. ManX has well-characterized
      specific interactions (homodimerization, interaction with HPr) that are captured by more
      specific terms.
    action: REMOVE
    reason: >-
      Per curation guidelines, "protein binding" (GO:0005515) is uninformative and does not
      convey meaningful functional information about ManX. The large-scale pull-down study
      (PMID:16606699) identifies interactions but the generic "protein binding" term does not
      add useful annotation. More specific interaction terms like GO:0042803 (protein
      homodimerization activity) are already annotated.
    supported_by:
      - reference_id: PMID:16606699
        supporting_text: >-
          A large-scale comprehensive pull-down assay was performed using a His-tagged Escherichia
          coli ORF clone library

- term:
    id: GO:0009401
    label: phosphoenolpyruvate-dependent sugar phosphotransferase system
  evidence_type: IDA
  original_reference_id: PMID:2951378
  review:
    summary: >-
      IDA annotation for PEP-dependent sugar PTS based on the seminal Erni et al. 1987 paper
      that characterized the mannose permease as consisting of three subunits mediating sugar
      transport and phosphorylation via the PTS (PMID:2951378).
    action: ACCEPT
    reason: >-
      Core biological process. Erni et al. 1987 demonstrated that the mannose permease mediates
      PEP-dependent sugar transport and phosphorylation (PMID:2951378). This is the primary
      function of ManX.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The mannose permease of the bacterial phosphotransferase system mediates sugar transport
          across the cytoplasmic membrane concomitant with sugar phosphorylation

- term:
    id: GO:0015761
    label: mannose transmembrane transport
  evidence_type: NAS
  original_reference_id: PMID:2951378
  review:
    summary: >-
      NAS annotation for mannose transmembrane transport. Erni et al. 1987 explicitly described
      the mannose permease as mediating mannose transport (PMID:2951378). ManX is the EIIAB
      component required for mannose transport and phosphorylation.
    action: ACCEPT
    reason: >-
      Mannose transport is the primary named function of the ManXYZ complex. Although ManX alone
      is not the transmembrane component (ManY/ManZ form the channel), ManX is essential for
      the transport-coupled phosphorylation. PMID:2951378 states all three subunits are required
      for sugar transport.
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          All three subunits are required for sugar transport and phosphorylation

- term:
    id: GO:0015761
    label: mannose transmembrane transport
  evidence_type: IDA
  original_reference_id: PMID:5545083
  review:
    summary: >-
      IDA annotation for mannose transmembrane transport based on Kundig & Roseman 1971
      (PMID:5545083), which characterized constitutive membrane-bound enzymes II of the E. coli
      PTS including the mannose-specific system.
    action: ACCEPT
    reason: >-
      This early characterization paper established the mannose-specific PTS enzyme II activity
      in E. coli membranes. ManX is essential for mannose transport by the ManXYZ complex.
    supported_by:
      - reference_id: PMID:5545083
        supporting_text: >-
          Sugar transport. II. Characterization of constitutive membrane-bound enzymes II of the
          Escherichia coli phosphotransferase system

- term:
    id: GO:0015764
    label: N-acetylglucosamine transport
  evidence_type: EXP
  original_reference_id: PMID:6252281
  review:
    summary: >-
      EXP annotation for N-acetylglucosamine transport. Jones-Mortimer & Kornberg 1980
      (PMID:6252281) showed that N-acetylglucosamine enters E. coli by two PTS systems,
      one of which is the PtsM (ManXYZ) system. This is a secondary transport substrate
      of the Man-PTS.
    action: KEEP_AS_NON_CORE
    reason: >-
      N-acetylglucosamine transport via the Man-PTS is experimentally documented (PMID:6252281)
      but represents a secondary substrate rather than the core mannose/glucose transport
      function. The Man-PTS has broad substrate specificity.
    supported_by:
      - reference_id: PMID:6252281
        supporting_text: >-
          N-Acetylglucosamine enters E. coli by two distinct phosphotransferase systems
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          the mannose-family PTS can be **promiscuous** in substrate handling beyond mannose

- term:
    id: GO:0098708
    label: D-glucose import across plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:5545083
  review:
    summary: >-
      IDA annotation for D-glucose import across plasma membrane. The Man-PTS is known to
      transport glucose in addition to mannose (PMID:2999119 mentions 2-deoxyglucose transport).
      Glucose is an important substrate of the Man-PTS.
    action: KEEP_AS_NON_CORE
    reason: >-
      Glucose transport by the Man-PTS is well established. Erni & Zanolari 1985 showed the
      mannose permease mediates transport of mannose, 2-deoxyglucose, and other hexoses
      (PMID:2999119). However, glucose transport is a secondary function; the primary named
      substrate is mannose.
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose,
          and a number of other hexoses
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          lists substrates associated with the ManXYZ PTS system including **mannose, glucose, 2-deoxyglucose, fructose**, and amino sugars (including **GlcNAc/GlcN**)

- term:
    id: GO:1990539
    label: fructose import across plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:4153999
  review:
    summary: >-
      EXP annotation for fructose import across plasma membrane. Ferenci & Kornberg 1974
      (PMID:4153999) studied PTS-mediated fructose phosphorylation in E. coli. The Man-PTS
      can transport fructose as a secondary substrate.
    action: KEEP_AS_NON_CORE
    reason: >-
      Fructose import via the Man-PTS is a secondary transport function. E. coli has a dedicated
      fructose PTS (FruAB), and fructose transport via the Man-PTS is a minor pathway. This is
      a legitimate but non-core annotation.
    supported_by:
      - reference_id: PMID:4153999
        supporting_text: >-
          The role of phosphotransferase-mediated syntheses of fructose 1-phosphate and fructose
          6-phosphate in the growth of Escherichia coli on fructose

- term:
    id: GO:1990539
    label: fructose import across plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:4154035
  review:
    summary: >-
      EXP annotation for fructose import based on Jones-Mortimer & Kornberg 1974 (PMID:4154035),
      a genetic analysis of fructose utilization showing the Man-PTS can participate in fructose
      uptake.
    action: KEEP_AS_NON_CORE
    reason: >-
      Duplicate of the fructose import annotation with a different reference. Fructose transport
      is a secondary substrate for the Man-PTS. Keeping as non-core.
    supported_by:
      - reference_id: PMID:4154035
        supporting_text: >-
          Genetical analysis of fructose utilization by Escherichia coli

- term:
    id: GO:0005829
    label: cytosol
  evidence_type: HDA
  original_reference_id: PMID:16858726
  review:
    summary: >-
      HDA annotation for cytosol localization based on complexomic study using 2D BN/SDS-PAGE
      (PMID:16858726). ManX was identified in the cytosolic fraction. Consistent with its known
      dual localization (cytoplasm and membrane-associated).
    action: ACCEPT
    reason: >-
      ManX is found in the cytosol as established by multiple approaches. The complexomic study
      (PMID:16858726) identified ManX in both cytosolic and membrane fractions, consistent with
      the biochemical evidence (PMID:2999119).
    supported_by:
      - reference_id: PMID:16858726
        supporting_text: >-
          the cytosolic and membrane protein complexes of Escherichia coli were separated
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm

- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:2999119
  review:
    summary: >-
      IDA annotation for cytoplasm localization. Erni & Zanolari 1985 (PMID:2999119) showed that
      IIIMan (ManX) exists both membrane-associated and free in the cytoplasm.
    action: ACCEPT
    reason: >-
      Well-supported localization. ManX is a soluble/peripheral protein found in the cytoplasm
      (PMID:2999119).
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm

- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: PMID:2999119
  review:
    summary: >-
      IDA annotation for cytosol localization based on Erni & Zanolari 1985 (PMID:2999119).
      ManX is found free in the cytoplasm/cytosol when not membrane-associated.
    action: ACCEPT
    reason: >-
      Consistent with the biochemical purification showing ManX exists as a soluble cytoplasmic
      protein (PMID:2999119). Cytosol is a reasonable specific localization for the free form.
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          ManX is annotated as **IM, C**, consistent with a **cytosolic/peripheral phosphotransfer component associated with the inner membrane complex**.

- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:2999119
  review:
    summary: >-
      IDA annotation for plasma membrane localization. Erni & Zanolari 1985 (PMID:2999119)
      showed ManX is found membrane-associated. UniProt confirms it is a peripheral membrane
      protein of the cell inner membrane.
    action: ACCEPT
    reason: >-
      Well-supported localization. ManX associates with the inner (plasma) membrane as a
      peripheral membrane protein (PMID:2999119). This represents one of its two localizations
      (cytoplasmic and membrane-associated).
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer and is found both membrane-associated and
          free in the cytoplasm

- term:
    id: GO:0009401
    label: phosphoenolpyruvate-dependent sugar phosphotransferase system
  evidence_type: IDA
  original_reference_id: PMID:2999119
  review:
    summary: >-
      IDA annotation for PEP-dependent sugar PTS based on Erni & Zanolari 1985 (PMID:2999119).
      This paper demonstrated PEP-dependent phosphorylation of IIIMan and reconstituted
      phosphotransferase activity in vitro.
    action: ACCEPT
    reason: >-
      Core biological process. The paper directly demonstrated PEP-dependent phosphorylation
      of ManX and reconstituted sugar phosphorylation activity (PMID:2999119).
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan can be phosphorylated in a phosphoenolpyruvate-dependent reaction

- term:
    id: GO:0016301
    label: kinase activity
  evidence_type: IDA
  original_reference_id: PMID:2999119
  review:
    summary: >-
      IDA annotation for kinase activity. ManX phosphorylates sugar substrates, which is a
      kinase activity. However, this is a very broad term. The more specific GO:0008982
      (protein-N(PI)-phosphohistidine-carbohydrate phosphotransferase activity) and GO:0022870
      (mannose-specific PTS transporter activity) better capture this function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      While ManX does have phosphotransferase (kinase-like) activity, GO:0016301 is too broad
      and does not capture the PTS-specific mechanism. ManX is not a conventional kinase; it
      transfers phosphoryl groups from phosphohistidine intermediates to sugars as part of the
      PTS system. The more specific terms GO:0008982 and GO:0022870 are already annotated and
      better represent this function. GO:0016301 could be misleading.
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIMan and IIIMan are both required for phosphorylation of 2-deoxyglucose in vitro

- term:
    id: GO:0022870
    label: protein-N(PI)-phosphohistidine-mannose phosphotransferase system transporter
      activity
  evidence_type: IDA
  original_reference_id: PMID:5545083
  review:
    summary: >-
      IDA annotation for mannose-specific PTS transporter activity. This is the most specific
      molecular function term for ManX, capturing both the mannose substrate specificity and the
      PTS phosphotransferase mechanism. ManX is the EIIAB phosphorylating subunit of the
      mannose-specific PTS (PMID:2951378, PMID:2999119).
    action: ACCEPT
    reason: >-
      This is the most informative and specific MF term for ManX. It captures the mannose-specific
      PTS transporter activity that is the core molecular function of the ManXYZ complex. Well
      supported by multiple studies (PMID:2951378, PMID:2999119, PMID:2681202, PMID:8262947).
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The mannose permease of the bacterial phosphotransferase system mediates sugar transport
          across the cytoplasmic membrane concomitant with sugar phosphorylation
      - reference_id: PMID:2999119
        supporting_text: >-
          It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose,
          and a number of other hexoses
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          ManX** is the **mannose-family PTS EIIAB subunit**. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a **cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components.

- term:
    id: GO:0042803
    label: protein homodimerization activity
  evidence_type: IDA
  original_reference_id: PMID:2951378
  review:
    summary: >-
      IDA annotation for protein homodimerization activity. ManX (IIIMan) forms homodimers as
      demonstrated by Erni et al. 1987 (PMID:2951378) and confirmed by Erni & Zanolari 1985
      (PMID:2999119) and structural studies. UniProt states "Homodimer" with multiple supporting
      references.
    action: ACCEPT
    reason: >-
      Well-supported molecular function. ManX forms stable homodimers, confirmed by biochemical
      purification (PMID:2999119), characterization studies (PMID:2951378), and NMR structural
      studies. Dimerization is functionally relevant as shown by mutagenesis (His-10 and other
      mutations abolish dimerization; PMID:8262947).
    supported_by:
      - reference_id: PMID:2999119
        supporting_text: >-
          IIIMan, a 35-kDa protein, exists as a dimer
      - reference_id: PMID:2951378
        supporting_text: >-
          IIIMan (35 kDa) is a hydrophilic protein which is transiently phosphorylated

- term:
    id: GO:0016020
    label: membrane
  evidence_type: HDA
  original_reference_id: PMID:16858726
  review:
    summary: >-
      HDA annotation for membrane localization based on the complexomic study (PMID:16858726).
      ManX was found in both cytosolic and membrane fractions. This is a broad CC term; the more
      specific GO:0005886 (plasma membrane) is also annotated.
    action: ACCEPT
    reason: >-
      Correct but broad. The complexomic study identified ManX in membrane fractions
      (PMID:16858726), consistent with its known peripheral membrane association (PMID:2999119).
      The more specific plasma membrane term is also annotated.
    supported_by:
      - reference_id: PMID:16858726
        supporting_text: >-
          the cytosolic and membrane protein complexes of Escherichia coli were separated
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: >-
    Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary
    mapping, accompanied by conservative changes to GO terms applied by UniProt
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: file:ECOLI/manX/manX-deep-research-falcon.md
  title: >-
    Falcon (Edison Scientific) deep research report: Functional annotation of manX
    (UniProt P69797) in Escherichia coli K-12
  findings:
    - statement: >-
        Falcon corroborates ManX as the cytosolic EIIAB phosphotransfer subunit of the
        mannose-family PTS, distinct from the membrane permease subunits ManY/ManZ.
      reference_section_type: OTHER
      supporting_text: |-
        ManX** is the **mannose-family PTS EIIAB subunit**. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a **cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components.
    - statement: >-
        Falcon corroborates the manXYZ operon organization, with manY and manZ encoding the
        membrane permease subunits of the complex.
      reference_section_type: OTHER
      supporting_text: |-
        Multiple sources explicitly place **manX** with **manY** and **manZ** in the **manXYZ** locus, where manY and manZ encode the membrane permease subunits.
    - statement: >-
        Falcon corroborates the broad/promiscuous substrate range of the Man-PTS beyond mannose,
        consistent with the secondary glucose, fructose, and N-acetylglucosamine transport
        annotations marked non-core in this review.
      reference_section_type: OTHER
      supporting_text: |-
        the mannose-family PTS can be **promiscuous** in substrate handling beyond mannose
    - statement: >-
        Falcon corroborates a substrate set including mannose, glucose, 2-deoxyglucose, fructose,
        and amino sugars (GlcNAc/GlcN) for the ManXYZ PTS system.
      reference_section_type: OTHER
      supporting_text: |-
        lists substrates associated with the ManXYZ PTS system including **mannose, glucose, 2-deoxyglucose, fructose**, and amino sugars (including **GlcNAc/GlcN**)
    - statement: >-
        Falcon corroborates the dual localization of ManX as a cytosolic/peripheral phosphotransfer
        component associated with the inner membrane complex.
      reference_section_type: OTHER
      supporting_text: |-
        ManX is annotated as **IM, C**, consistent with a **cytosolic/peripheral phosphotransfer component associated with the inner membrane complex**.
- id: PMID:16606699
  title: Large-scale identification of protein-protein interaction of Escherichia coli K-12.
  findings:
    - statement: >-
        Large-scale pull-down assay using His-tagged E. coli ORF clone library identified
        protein-protein interactions for 2667 bait proteins. ManX interaction with CytR was
        identified. This is a high-throughput study and individual interactions should be treated
        with caution.
- id: PMID:16858726
  title: >-
    A complexomic study of Escherichia coli using two-dimensional blue native/SDS polyacrylamide
    gel electrophoresis.
  findings:
    - statement: >-
        Complexomic study separated cytosolic and membrane protein complexes of E. coli. ManX
        was identified in both cytosolic and membrane fractions, consistent with its known dual
        localization.
- id: PMID:2951378
  title: >-
    The mannose permease of Escherichia coli consists of three different proteins. Amino acid
    sequence and function in sugar transport, sugar phosphorylation, and penetration of phage
    lambda DNA.
  findings:
    - statement: >-
        Demonstrated that the mannose permease consists of three subunits (IIIMan/ManX, II-PMan/ManY,
        II-MMan/ManZ) encoded in a single transcriptional unit. All three are required for sugar
        transport and phosphorylation. ManX (IIIMan, 35 kDa) is a hydrophilic protein that is
        transiently phosphorylated and contains the active site for sugar phosphorylation. The
        permease also functions as a receptor for bacterial chemotaxis and is required for
        bacteriophage lambda DNA penetration (II-PMan and II-MMan are sufficient for lambda DNA
        penetration).
- id: PMID:2999119
  title: >-
    The mannose-permease of the bacterial phosphotransferase system. Gene cloning and purification
    of the enzyme IIMan/IIIMan complex of Escherichia coli.
  findings:
    - statement: >-
        Cloned ptsM and ptsL genes and purified IIMan/IIIMan complex. IIIMan (ManX, 35 kDa) exists
        as a dimer, found both membrane-associated and free in the cytoplasm. IIIMan can be
        phosphorylated in a PEP-dependent reaction. Both IIMan and IIIMan are required for
        phosphorylation of 2-deoxyglucose in vitro.
- id: PMID:2681202
  title: >-
    Mannose permease of Escherichia coli. Domain structure and function of the phosphorylating
    subunit.
  findings:
    - statement: >-
        Demonstrated that ManX (EIIAB) has two phosphorylation sites: His-10 in the EIIA domain
        (phosphorylated by HPr) and His-175 in the EIIB domain (phosphorylated by EIIA). The
        protein consists of distinct EIIA and EIIB domains connected by a hinge region.
- id: PMID:8262947
  title: >-
    The mannose transporter of Escherichia coli. Structure and function of the IIABMan subunit.
  findings:
    - statement: >-
        Mutagenesis studies confirmed His-10 and His-175 as active site residues. H10C and H175C
        mutations abolish phosphotransferase activity. H10C also prevents dimerization. H86N
        mutation abolishes activity, indicating His-86 involvement in phosphoryl transfer between
        the two domains. EC 2.7.1.191 catalytic activity confirmed.
- id: PMID:4153999
  title: >-
    The role of phosphotransferase-mediated syntheses of fructose 1-phosphate and fructose
    6-phosphate in the growth of Escherichia coli on fructose.
  findings:
    - statement: >-
        Studied PTS-mediated fructose phosphorylation pathways in E. coli growth on fructose.
        The Man-PTS can participate in fructose uptake as a secondary substrate.
- id: PMID:4154035
  title: Genetical analysis of fructose utilization by Escherichia coli.
  findings:
    - statement: >-
        Genetic analysis of fructose utilization pathways showing multiple PTS systems can
        transport fructose in E. coli.
- id: PMID:5545083
  title: >-
    Sugar transport. II. Characterization of constitutive membrane-bound enzymes II of the
    Escherichia coli phosphotransferase system.
  findings:
    - statement: >-
        Early characterization of constitutive membrane-bound PTS enzymes II in E. coli,
        including the mannose-specific system.
- id: PMID:6252281
  title: Amino-sugar transport systems of Escherichia coli K12.
  findings:
    - statement: >-
        Demonstrated that N-acetylglucosamine enters E. coli by two PTS systems, one being
        the PtsM (Man-PTS) system. Glucosamine, mannose and 2-deoxyglucose also enter via PtsM.
- id: PMID:4604906
  title: >-
    Phosphotransferase-system enzymes as chemoreceptors for certain sugars in Escherichia coli
    chemotaxis.
  findings:
    - statement: >-
        Demonstrated that PTS enzymes, including the mannose PTS, function as chemoreceptors
        for sugar chemotaxis in E. coli.
- id: PMID:353494
  title: >-
    E. coli K-12 pel mutants, which block phage lambda DNA injection, coincide with ptsM,
    which determines a component of a sugar transport system.
  findings:
    - statement: >-
        Showed that pel mutants blocking phage lambda DNA injection map to ptsM, establishing
        the Man-PTS as the receptor for lambda DNA penetration.
core_functions:
  - description: >-
      ManX is the EIIAB phosphorylating subunit of the mannose-specific PTS. It receives a
      phosphoryl group from HPr at His-10 (EIIA domain), transfers it internally to His-175
      (EIIB domain), and then to the sugar substrate during transport by the ManXYZ complex.
      This is the primary molecular function of ManX (PMID:2681202, PMID:8262947, PMID:2951378).
    molecular_function:
      id: GO:0022870
      label: protein-N(PI)-phosphohistidine-mannose phosphotransferase system transporter activity
    directly_involved_in:
      - id: GO:0009401
        label: phosphoenolpyruvate-dependent sugar phosphotransferase system
      - id: GO:0015761
        label: mannose transmembrane transport
    locations:
      - id: GO:0005829
        label: cytosol
      - id: GO:0005886
        label: plasma membrane
    in_complex:
      id: GO:1902495
      label: transmembrane transporter complex
    supported_by:
      - reference_id: PMID:2951378
        supporting_text: >-
          The mannose permease of the bacterial phosphotransferase system mediates sugar transport
          across the cytoplasmic membrane concomitant with sugar phosphorylation
      - reference_id: PMID:2999119
        supporting_text: >-
          It mediates active transport concomitant with phosphorylation of mannose, 2-deoxyglucose,
          and a number of other hexoses
      - reference_id: file:ECOLI/manX/manX-deep-research-falcon.md
        supporting_text: |-
          ManX** is the **mannose-family PTS EIIAB subunit**. In curated annotations, it is associated with the inner-membrane system but is itself annotated as a **cytosolic component (IM, C)**, consistent with a cytosolic phosphotransfer function that operates in conjunction with inner-membrane permease components.
suggested_questions:
  - question: >-
      Should the chemoreceptor function of the Man-PTS (sugar chemotaxis) be annotated for ManX
      specifically, or is this a property of the complex? Adler & Epstein 1974 (PMID:4604906)
      showed PTS enzymes serve as chemoreceptors.
  - question: >-
      Should the role in bacteriophage lambda DNA injection be annotated? The pel mutant phenotype
      maps to the Man-PTS (PMID:353494), but ManY/ManZ (not ManX) are sufficient for lambda DNA
      penetration (PMID:2951378).
  - question: >-
      Is the GO:0016301 (kinase activity) annotation appropriate for a PTS phosphotransferase,
      or is this misleading given that the mechanism involves phosphohistidine intermediates
      rather than conventional kinase activity?

manX

Gene Description

Existing Annotations Review

Core Functions

References

Suggested Questions for Experts

Deep Research

Falcon

Research report: Functional annotation of manX (UniProt P69797) in Escherichia coli K-12

0) Identity verification (critical disambiguation)

1) Key concepts and current understanding

1.1 The PTS and mannose-family Enzyme II systems

1.2 What ManX is (definition)

1.3 Reaction catalyzed and mechanistic role

2) Substrate specificity and physiological role

2.1 Substrate range

2.2 Biological processes and pathway context

3) Cellular localization and complex organization

4) Recent developments (prioritizing 2023–2024)

4.1 2023: Transport engineering perspective (systems-level view)

4.2 2024: Regulatory rewiring can transform mannose ‘nutrient quality’

4.3 2024: PTS-linked global regulation (Cra)

5) Current applications and real-world implementations

5.1 Metabolic engineering and transport engineering

5.2 Glyco-/amino-sugar and analog uptake constraints (engineering context)

6) Expert opinions and analysis (authoritative sources)

7) Relevant statistics and recent quantitative data

8) Visual evidence (figure support)

9) Summary table (evidence-backed functional annotation)

10) Evidence gaps and limits of this retrieval

Key references (with dates and URLs)

Artifacts

Citations

📚 Additional Documentation

Notes

ManX (EIIAB-Man) - Research Notes

Summary

Key findings

Domain structure and phosphorylation

Dimerization

Localization

Substrate specificity

Regulation

Additional functions

Review decisions

📄 View Raw YAML