ptsI of Escherichia coli K-12 encodes enzyme I (EI), the general, non-sugar-specific first component of the phosphoenolpyruvate (PEP)-dependent sugar phosphotransferase system (PTS). The cytoplasmic homodimer has an N-terminal HPr-binding domain, a central domain carrying the phosphorylated His189 and a C-terminal PEP-binding domain. EI autophosphorylates from PEP in an Mg(2+)-dependent reaction and transfers the phosphoryl group to His15 of HPr, which feeds the sugar-specific Enzyme II complexes. EI also phosphorylates the HPr-like domain of the fructose multiphosphoryl transfer protein FPr, so it initiates fructose PTS uptake as well as uptake of glucose and other PTS sugars. EI concentrates near the cell pole, where the pole-localizer TmaR sequesters it and so modulates sugar uptake.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:17051159 Visualization of transient encounter complexes in protein-pr... | REMOVE | Summary: NMR paramagnetic relaxation study of transient encounter complexes between the EI N-terminal domain and HPr. Reason: The EI-HPr contact is the substrate interaction of the phosphotransferase activity already captured by GO:0008965, so bare protein binding adds no functional information. Removal follows the project protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:17053069 a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr |
| GO:0005515 protein binding | IPI PMID:20080627 Mechanistic details of a protein-protein association pathway... | REMOVE | Summary: Paramagnetic relaxation enhancement titrations of the EIN-HPr association pathway. Reason: The EI-HPr contact is the substrate interaction of the phosphotransferase activity already captured by GO:0008965, so bare protein binding adds no functional information. Removal follows the project protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:17053069 a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr |
| GO:0005515 protein binding | IPI PMID:20924357 Spatial and temporal organization of the E. coli PTS compone... | REMOVE | Summary: EI interacts with the antiterminator BglG and affects its subcellular localization. Reason: The EI-BglG interaction is phosphorylation-independent and its mechanism in bgl operon control is unknown; bare protein binding names no function. Removal follows the protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:20924357 we show that EI and HPr interact with BglG and affect its subcellular localization in a phosphorylation-independent manner |
| GO:0005515 protein binding | IPI PMID:22673508 Active site phosphoryl groups in the biphosphorylated phosph... | REMOVE | Summary: NMR of the biphosphorylated EIN-HPr phosphotransfer complex. Reason: The EI-HPr contact is the substrate interaction of the phosphotransferase activity already captured by GO:0008965, so bare protein binding adds no functional information. Removal follows the project protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:17053069 a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr |
| GO:0005515 protein binding | IPI PMID:33376208 Tyrosine phosphorylation-dependent localization of TmaR that... | REMOVE | Summary: EI binds the pole-localizer protein TmaR, which sequesters it at the cell pole. Reason: The interaction regulates EI by sequestration; it is a property of TmaR's function rather than an EI activity, and bare protein binding is uninformative. Removal follows the protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:33376208 TmaR is shown here to control the subcellular localization and activity of the general PTS protein Enzyme I (EI) by binding and polar sequestration of EI |
| GO:0005515 protein binding | IPI PMID:9109646 Identification by NMR of the binding surface for the histidi... | REMOVE | Summary: NMR mapping of the HPr binding surface on the EI N-terminal domain. Reason: The EI-HPr contact is the substrate interaction of the phosphotransferase activity already captured by GO:0008965, so bare protein binding adds no functional information. Removal follows the project protein-binding policy and does not deny the interaction. Supporting Evidence: PMID:17053069 a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr |
| GO:0005737 cytoplasm | EXP PMID:33376208 Tyrosine phosphorylation-dependent localization of TmaR that... | MODIFY | Summary: Szoke et al. imaged EI, showing polar localization controlled by TmaR binding and by EI tyrosine phosphorylation. Reason: Correct but general. The imaging shows a polar but cytoplasmic, non-membrane distribution of a soluble enzyme, which is compatible with the cytosol location supported by the cytosolic complexome fraction (HDA row); the row is refined to cytosol, which this gene already carries. Polar sequestration by TmaR is a distribution within the cytosol, not a separate compartment. Proposed replacements: cytosol Supporting Evidence: PMID:33376208 TmaR is shown here to control the subcellular localization and activity of the general PTS protein Enzyme I (EI) by binding and polar sequestration of EI |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | MODIFY | Summary: UniProt subcellular location, cytoplasm, mapped from an experimentally supported record line. Reason: Correct but general. EI has no membrane or signal feature, is a soluble enzyme acting on soluble HPr, and was recovered in the cytosolic complexome fraction (HDA row, PubMed:16858726); cytoplasm is refined to cytosol, which this gene already carries. Follows the E. coli ptsN precedent for the same GO_REF:0000044 row. Proposed replacements: cytosol Supporting Evidence: file:ECOLI/ptsI/ptsI-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:33376208}. |
| GO:0005829 cytosol | HDA PMID:16858726 A complexomic study of Escherichia coli using two-dimensiona... | ACCEPT | Summary: EI was identified among cytosolic protein complexes in a blue native/SDS-PAGE complexome of E. coli. Reason: High-throughput fractionation places EI in the soluble fraction, consistent with a cytosolic enzyme that phosphorylates soluble HPr. Supporting Evidence: PMID:16858726 the cytosolic and membrane protein complexes of Escherichia coli were separated |
| GO:0008965 phosphoenolpyruvate-protein phosphotransferase activity | EXP PMID:12705838 Enzyme I of the phosphotransferase system: induced-fit proto... | ACCEPT | Summary: Garcia-Alles et al. measured PEP-dependent activity of purified EI and of the C502A variant, defining Cys502 as the acid-base catalyst of the PEP site. Reason: Direct enzymology of purified E. coli EI with PEP as phosphoryl donor. Supporting Evidence: PMID:12705838 EI(C502A) is 10 000 times less active than wild-type EI [EI(wt)] with PEP as the substrate |
| GO:0008965 phosphoenolpyruvate-protein phosphotransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT places PEP-protein phosphotransferase activity at the bacterial root node PTN000532509 of PTHR46244, seeded by E. coli EI itself and by EI(Ntr) PtsP. Reason: EI catalyses the EC 2.7.3.9 reaction directly (kinetics in PubMed:12705838). Its own experimental annotation is one of the node seeds, which is expected for an IBD; the IBA adds that the activity is inherited across the enzyme I family. Supporting Evidence: file:ECOLI/ptsI/ptsI-uniprot.txt Enzyme I transfers the phosphoryl group from phosphoenolpyruvate (PEP) to the phosphoryl carrier protein (HPr) |
| GO:0008965 phosphoenolpyruvate-protein phosphotransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined electronic mapping from the PTS EI InterPro signature, Rhea 23880 and EC 2.7.3.9. Reason: The UniProt catalytic activity behind the mapping rests on direct kinetic evidence for this protein. Supporting Evidence: file:ECOLI/ptsI/ptsI-uniprot.txt KM=0.14 mM for PEP |
| GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro PTS EI signatures map to the PEP-dependent sugar PTS. Reason: EI is the general first component of the sugar PTS; this is its core process. Supporting Evidence: PMID:17053069 Sugar translocation initiates with the Mg(2+)-dependent phosphorylation of enzyme I (EI) by PEP. |
| GO:0015764 N-acetylglucosamine transport | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: PAINT places N-acetylglucosamine transport at root node PTN000532509, seeded only by Pseudomonas aeruginosa PA3760 (Q9HXN5), a fused EI-HPr-EIIA protein. Reason: E. coli EI is the general enzyme I: through HPr it feeds every sugar-specific Enzyme II, including the N-acetylglucosamine permease, so the claim is not wrong. But the GO convention for the general energy-coupling proteins is the general process GO:0009401, not one transport term per PTS sugar: E. coli HPr (P0AA04), which stands in the identical role, carries GO:0009401 and no N-acetylglucosamine or other sugar-specific transport term in GOA, and EI carries GO:0015764 only through this single IBA. The PTHR46244 family review rates the node TOO_DEEP for this term. Retaining one sugar out of many would be an arbitrary over-annotation, so the row is marked as such, consistent with the same node on Xanthomonas FruB. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000532509 · PANTHER:PTN000532509 SUPPORTS SOURCE BUT NOT TARGET Root bacterial node; assessed TOO_DEEP for GO:0015764 in the PTHR46244 family review because it also covers EI(Ntr). UniProtKB:Q9HXN5 · PA3760 SUPPORTS SOURCE BUT NOT TARGET Seed is an N-acetylglucosamine PTS multiphosphoryl protein; E. coli EI participates via HPr and NagE rather than by descent from that clade. Supporting Evidence: file:ECOLI/ptsI/ptsI-uniprot.txt General (non sugar-specific) component of the phosphoenolpyruvate-dependent sugar phosphotransferase system (sugar PTS). |
| GO:0016772 transferase activity, transferring phosphorus-containing groups | IEA GO_REF:0000002 | MODIFY | Summary: InterPro PEP-utilizing enzyme signatures map to the broad phosphorus-group transferase term. Reason: True but general; refine to the specific PEP-protein phosphotransferase activity already accepted on the experimental rows of this gene. Proposed replacements: phosphoenolpyruvate-protein phosphotransferase activity Supporting Evidence: PMID:12705838 EI(C502A) is 10 000 times less active than wild-type EI [EI(wt)] with PEP as the substrate |
| GO:0042802 identical protein binding | IPI PMID:16858726 A complexomic study of Escherichia coli using two-dimensiona... | KEEP AS NON CORE | Summary: EI was recovered as a homomultimeric complex in the blue native complexome. Reason: EI is a homodimer and dimerization is the functional state for PEP-dependent autophosphorylation; self-association is real but supports, rather than constitutes, the phosphotransferase function. Supporting Evidence: PMID:16858726 50 heteromultimeric and 256 homomultimeric protein complexes were found |
| GO:0042802 identical protein binding | IPI PMID:17053069 Structure of phosphorylated enzyme I, the phosphoenolpyruvat... | KEEP AS NON CORE | Summary: The crystal structure of phosphorylated EI is a dimer. Reason: As for the complexome row, homodimerization is supported structurally and is an accessory property of the catalytic enzyme. Supporting Evidence: PMID:17053069 The crystal structure reveals a dimeric protein |
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Download this section (compressed HTML)Q: Does EI phosphorylate the HPr-like domain of FPr with kinetics comparable to HPr in vivo, and does TmaR-mediated polar sequestration of EI change fructose uptake relative to glucose uptake?
Experiment: Compare fructose and glucose PTS uptake rates in tmaR deletion and overexpression strains, and measure EI-to-FPr versus EI-to-HPr phosphotransfer rates with purified proteins.
Type: transport assay and in vitro phosphotransfer kinetics
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