PctA (PA4309) is the major amino acid chemoreceptor of Pseudomonas aeruginosa PAO1, a methyl-accepting chemotaxis protein (MCP) encoded in the pctC-pctA-pctB region. It is an inner-membrane receptor with two transmembrane helices flanking a periplasmic dCache_1 (double PDC) ligand binding region, followed by a cytoplasmic HAMP domain and the MCP signalling domain. The ligand binding region binds 17 L-amino acids directly at its membrane-distal module, and PctA mediates chemotaxis towards nearly all proteinogenic L-amino acids except L-Gln and L-Asp. PctA also contributes to repellent responses to trichloroethylene, chloroform and methylthiocyanate, and to chemotaxis to histamine and the quorum-sensing signal autoinducer-2. Its paralogues PctB and PctC arose from pctA duplications and have narrower ligand ranges.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004888 transmembrane signaling receptor activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO transmembrane signaling receptor activity from the MCP family signature. Reason: Core molecular function. The periplasmic dCache_1 ligand binding region binds 17 L-amino acids directly, and the receptor mediates chemotaxis to them through its cytoplasmic HAMP-MCP signalling region: ligand binding outside and signalling inside. Supporting Evidence: PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. file:PSEAE/pctA/pctA-uniprot.txt PF02743; dCache_1 |
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: Plasma membrane from the UniProt subcellular location (cell inner membrane). Reason: Two transmembrane helices bracket the periplasmic ligand binding region, the standard inner-membrane topology of an MCP. Supporting Evidence: file:PSEAE/pctA/pctA-uniprot.txt Cell inner membrane {ECO:0000305}; Multi-pass PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. |
| GO:0006935 chemotaxis | IBA GO_REF:0000033 | ACCEPT | Summary: Chemotaxis propagated from PAINT node PTN001280296 (PTHR32089 MCP clade, 215 leaves in 22 taxa). PctA is one of the ten IBD seeds through its PseudoCAP IMP row; the node is assessed in the pctB notes. Reason: Core process. PctA is the major amino acid chemoreceptor of P. aeruginosa, and the IBD also rests on independent experimentally characterized MCPs. The target in its own WITH/FROM reflects its own experimental row, which is expected. Supporting Evidence: PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. |
| GO:0006935 chemotaxis | IEA GO_REF:0000120 | ACCEPT | Summary: Chemotaxis from the MCP family signature (UniProt combined automatic rule). Reason: Consistent with the experimental and IBA rows. Supporting Evidence: PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. |
| GO:0006935 chemotaxis | IMP PMID:9353923 Genetic identification of chemotactic transducers for amino ... | ACCEPT | Summary: PseudoCAP IMP seed for the IBD at PTN001280296. The deletion strain PCT2 (lacking pctC-orf1-pctA-pctB) shows no taxis to any of the 20 L-amino acids, and plasmid-borne pctA restores taxis to 18 of them. Reason: Seed verdict SOUND. Loss of amino acid taxis and its restoration by the cloned gene, for a receptor whose ligand binding region binds the same amino acids (PMID:23650915), show that PctA performs the sensing step of chemotaxis itself. Supporting Evidence: PMID:9353923 A null mutant strain PCT2, which contained a deletion in the entire pctC, orf1, pctA and pctB genes, did not show chemotaxis towards all 20 commonly occurring L-amino acids. PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. |
| GO:0007165 signal transduction | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO signal transduction from the HAMP and MCP signalling domains. Reason: Correct but general. PctA binds its ligands in the periplasm and signals across the inner membrane to the chemosensory array, so cell surface receptor signaling pathway (an is_a descendant) is the specific term, as chosen for pctB. Proposed replacements: cell surface receptor signaling pathway Supporting Evidence: PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. file:PSEAE/pctA/pctA-uniprot.txt PF00015; MCPsignal |
| GO:0016020 membrane | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO membrane location. Reason: True but uninformative; GO:0005886 plasma membrane, accepted on this gene, is an is_a descendant and entails it. Supporting Evidence: file:PSEAE/pctA/pctA-uniprot.txt Cell inner membrane {ECO:0000305}; Multi-pass |
| GO:0016597 amino acid binding | IDA PMID:23650915 Paralogous chemoreceptors mediate chemotaxis towards protein... | ACCEPT | Summary: Direct binding of 17 L-amino acids to the recombinant ligand binding region; ligands bind the membrane-distal PDC module. Reason: Direct binding assay on the purified sensor domain; ligand recognition is the receptor sensing activity. Crystal structures of the ligand binding region with bound amino acids are available (5LTX, 5T65, 5T7M). Supporting Evidence: PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. file:PSEAE/pctA/pctA-uniprot.txt The ligand binding region binds directly to 17 L-amino acids. |
| GO:0016597 amino acid binding | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA amino acid binding. Reason: Consistent with the IDA row for the same term. Supporting Evidence: PMID:23650915 We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. |
| GO:0043200 response to amino acid | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA response to amino acid. Reason: Consistent with the IMP row; GO has no amino-acid-specific chemotaxis term, so this term with chemotaxis is as precise as the ontology allows. Supporting Evidence: PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. |
| GO:0043200 response to amino acid | IMP PMID:9353923 Genetic identification of chemotactic transducers for amino ... | ACCEPT | Summary: PseudoCAP IMP; complementation of the pct deletion mutant by pctA restores chemotactic responses to 18 L-amino acids. Reason: The response measured is chemotaxis to amino acids, mediated by the receptor that binds them; with chemotaxis this is the most precise available pairing. Supporting Evidence: PMID:9353923 The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. aeruginosa. |
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Download this section (compressed HTML)Experiment: Measure chemotaxis of pctA ligand binding site mutants (residues contacting the amino acid in the 5T65 and 5LTX structures) to separate direct ligand binding from the indirect histamine response.
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