mluA

UniProt ID: C5B1I1
Organism: Methylorubrum extorquens AM1
Review Status: DRAFT
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Gene Description

TonB-dependent outer membrane receptor (locus MexAM1_META1p4129) of the TonB-dependent receptor family. Reported as mluA (methylolanthanin uptake A) within the mll cluster, functioning in active uptake of a lanthanide-metallophore (methylolanthanin) complex across the outer membrane into the periplasm, and as a cell-surface signaling receptor that couples to the anti-sigma factor MluR. Note that primary-literature retrieval for the bare accession C5B1I1 is sparse and the family-level mechanism (outer-membrane, TonB/ExbB/ExbD-energized uptake of a scarce metal-chelate substrate delivered to the periplasm) is the most robustly supported function; the specific lanthanide-metallophore substrate assignment rests on the mll-cluster characterization.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0006826 iron ion transport
IEA
GO_REF:0000043
REMOVE
Summary: Incorrect substrate. This TonB-dependent receptor is not an iron transporter; it is implicated in uptake of a lanthanide-metallophore complex, and even at the family level the substrate of this specific accession cannot be assigned as iron. The keyword-derived iron transport annotation reflects generic TonB/siderophore-family inference, not iron specificity.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
there is no locus-specific genetic/biochemical evidence in the retrieved corpus identifying the precise ligand for UniProt C5B1I1 in AM1
GO:0009279 cell outer membrane
IEA
GO_REF:0000120
ACCEPT
Summary: Correct. As a TonB-dependent receptor of the TonB-dependent receptor family, the protein is an integral outer membrane beta-barrel transporter. Both deep-research sources concur on outer-membrane localization, consistent with the UniProt subcellular location annotation.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
Thus C5B1I1 should be localized to the
file:METEA/mluA/mluA-deep-research-perplexity.md
the protein is an integral outer membrane protein with the characteristic 22-stranded Ξ²-barrel structure typical of this protein family
GO:0015343 siderophore-iron transmembrane transporter activity
IEA
GO_REF:0000002
MODIFY
Summary: Wrong specificity but correct general activity. The protein is a TonB-dependent active uptake transporter, but the substrate is a lanthanide-metallophore, not an iron-siderophore. Rather than removing the transporter activity outright, generalize to transmembrane transporter activity (the iron-siderophore reaction defined for this term does not apply). The family-level uptake-transporter function is well supported; the precise ligand is not iron.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
C5B1I1 most likely functions as an
file:METEA/mluA/mluA-deep-research-falcon.md
the substrate should be reported as
GO:0015344 siderophore uptake transmembrane transporter activity
IEA
GO_REF:0000118
MODIFY
Summary: Wrong specificity but correct general activity. The TreeGrafter-propagated iron-siderophore uptake term over-specifies the substrate. The protein performs TonB-energized active uptake transport, but of a lanthanide-metallophore rather than an iron-siderophore; generalize to transmembrane transporter activity.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
they mediate uptake of substrates
GO:0015891 siderophore transport
IEA
GO_REF:0000002
REMOVE
Summary: Incorrect specificity. Siderophore transport is defined as movement of low-molecular-weight Fe(III)-chelating substances. This receptor is implicated in uptake of a lanthanide-metallophore complex (methylolanthanin), not an Fe(III) siderophore, so the term is inappropriate as an over-specific substrate assignment.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
the substrate should be reported as
GO:0019867 outer membrane
IEA
GO_REF:0000002
KEEP AS NON CORE
Summary: Correct but less specific than the cell outer membrane annotation. The protein is an outer-membrane TonB-dependent beta-barrel transporter; the Gram-negative cell outer membrane term (GO:0009279) is preferred and is already ACCEPTed and used in core_functions. Keep this broader term as non-core because it is redundant with the more specific GO:0009279 for core representation.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
Thus C5B1I1 should be localized to the
GO:0033214 siderophore-iron import into cell
IEA
GO_REF:0000120
REMOVE
Summary: Incorrect substrate. This term describes import of Fe(III) solubilized by ferric-iron-specific siderophores. The receptor imports a lanthanide-metallophore complex into the periplasm, not siderophore-iron, so the term is inappropriate.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-falcon.md
there is no locus-specific genetic/biochemical evidence in the retrieved corpus identifying the precise ligand for UniProt C5B1I1 in AM1
GO:0038023 signaling receptor activity
IEA
GO_REF:0000002
KEEP AS NON CORE
Summary: Plausible and supported. TonB-dependent receptors of this signaling subtype possess an N-terminal signaling (Secretin/TonB short N-terminal) domain; for this protein the mll-cluster work describes a cell-surface signaling system in which the receptor interacts with the anti-sigma factor MluR upon ligand binding. Keep as a non-core signaling-receptor function alongside the core uptake-transport role; the review itself characterizes this as ancillary to the primary metal-chelate uptake-transport function.
Supporting Evidence:
file:METEA/mluA/mluA-deep-research-perplexity.md
The protein contains an N-terminal signaling domain that interacts with the anti-sigma factor MluR, encoded by the adjacent *mluR* gene within the same operon

Core Functions

TonB-dependent active uptake of a scarce extracellular metal-chelate substrate (reported lanthanide-metallophore/methylolanthanin complex) across the outer membrane into the periplasm, energized by the TonB-ExbB-ExbD system.

Cellular Locations:
Supporting Evidence:
  • file:METEA/mluA/mluA-deep-research-falcon.md
    C5B1I1 most likely functions as an
  • file:METEA/mluA/mluA-deep-research-falcon.md
    in methylotrophs, TBDTs frequently function in **metal acquisition** by importing **chelated metal complexes** to the periplasm

Cell-surface signaling receptor that, upon ligand binding, transduces a signal via its N-terminal signaling domain to the cognate anti-sigma factor MluR, coupling extracellular metal sensing to gene regulation.

Molecular Function:
signaling receptor activity
Cellular Locations:
Supporting Evidence:
  • file:METEA/mluA/mluA-deep-research-perplexity.md
    The protein contains an N-terminal signaling domain that interacts with the anti-sigma factor MluR, encoded by the adjacent *mluR* gene within the same operon

References

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Deep Research

Falcon

(mluA-deep-research-falcon.md)

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Perplexity

(mluA-deep-research-perplexity.md)

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