PP_4332 encodes the canonical CheW coupling protein of the flagellar chemotaxis gene cluster of Pseudomonas putida KT2440. It is a small (159 aa) soluble protein consisting of a single CheW domain (two SH3-like beta-barrel subdomains) and belongs to the CheW subfamily of the CheA/CheW family. By homology with E. coli CheW, it acts as an adaptor that binds both the cytoplasmic tips of methyl-accepting chemotaxis receptors and the P5 regulatory domain of the histidine kinase CheA, assembling receptor-CheW-CheA core signaling units and the extended chemoreceptor arrays in which receptors activate and control CheA autophosphorylation. KT2440 encodes a second, adjacent CheW-domain protein (PP_4333) whose relationship to PP_4332 is unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005829 cytosol | IEA GO_REF:0000118 | ACCEPT | Summary: TreeGrafter propagation from the PANTHER CheW subfamily node. CheW is a soluble cytoplasmic protein that functions at the cytoplasmic face of membrane chemoreceptor arrays. Reason: The protein has no transmembrane segment or signal peptide and consists solely of the CheW-like domain, consistent with a cytosolic location. CheW in E. coli acts in cytoplasmic complexes with CheA and the receptor cytoplasmic domains. No KT2440 localization study refines this (e.g. to a polar array), so cytosol is kept, consistent with the soluble relay proteins of this pathway. Supporting Evidence: file:PSEPK/PP_4332/PP_4332-uniprot.txt FT DOMAIN 13..153 FT /note="CheW-like" file:PSEPK/PP_4332/PP_4332-uniprot.txt DR PANTHER; PTHR22617:SF23; CHEMOTAXIS PROTEIN CHEW; 1. PMID:1992467 we report direct measurement of a physical interaction between CheW and CheA |
| GO:0006935 chemotaxis | IEA GO_REF:0000120 | ACCEPT | Summary: CheW is an essential core component of the chemotaxis signaling complex; PP_4332 is the CheW of the KT2440 flagellar chemotaxis cluster. Reason: CheW does part of the work of chemotaxis: it couples receptors to CheA within the ternary signaling complex. E. coli CheW variants unable to bind Tar or CheA cannot form active ternary complexes and cannot mediate chemotaxis. PP_4332 is a member of the CheW subfamily (InterPro IPR039315, PANTHER PTHR22617:SF23) and is listed as the CheW of the KT2440 core cascade in the module synthesis. No KT2440 PP_4332 mutant phenotype is in the cached literature. Supporting Evidence: PMID:11923283 mutations which eliminate CheW binding to Tar (V36M) or to CheA (G57D) result in a complete inability to form active ternary complexes in vitro and render the CheW protein incapable of mediating chemotaxis in vivo file:PSEPK/PP_4332/PP_4332-uniprot.txt DR InterPro; IPR039315; CheW. file:projects/P_PUTIDA/deep-research/PSEPK__bacterial_chemotaxis_signal_transduction__ppu02030-deep-research-openscientist.md CheA (PP_4338) autophosphorylation, via CheW (PP_4332/PP_4333) coupling |
| GO:0007165 signal transduction | IEA GO_REF:0000002 | MODIFY | Summary: True but general. CheW acts in the chemotaxis His-Asp phosphorelay by coupling receptor signaling to CheA autophosphorylation. Reason: Correct but general. CheW is required for receptor-controlled activation of CheA autophosphorylation, the first step of the chemotaxis phosphorelay; the specific process is phosphorelay signal transduction system (GO:0000160, a descendant of signal transduction). Proposed replacements: phosphorelay signal transduction system Supporting Evidence: PMID:1992467 An essential step in the signal transduction pathway of Escherichia coli is the control of the protein kinase activity of CheA by the chemotaxis receptor proteins. This control requires the participation of the CheW protein. PMID:21606342 Bacterial chemoreceptors, histidine kinase CheA, and coupling protein CheW form clusters of chemotaxis signaling complexes. |
| GO:0060090 molecular adaptor activity | ISS PMID:11923283 CheW binding interactions with CheA and Tar. Importance for ... | NEW | Summary: Proposed new MF: CheW is the adaptor that bridges chemoreceptors and CheA in the ternary signaling complex. Inferred from E. coli CheW (P0A964) through CheW-subfamily membership. Reason: GOA has no MF for PP_4332. E. coli CheW binds both CheA and the Tar receptor and these binding interactions are each required for active ternary complex formation and chemotaxis, matching the GO definition of molecular adaptor activity (brings together two or more molecules through selective non-covalent interactions so they function in a coordinated way). PP_4332 is a single-domain CheW of the CheW subfamily (PANTHER PTHR22617:SF23; InterPro IPR039315), not a CheA- or CheV-type CheW-domain fusion, so the adaptor role is transferred by ISS with E. coli CheW as the with/from. This is the module-asserted function for CheW. Supporting Evidence: PMID:11923283 Because CheW can bind to CheA and to Tar, it is thought to serve as an adapter protein in this complex. PMID:11923283 mutations which eliminate CheW binding to Tar (V36M) or to CheA (G57D) result in a complete inability to form active ternary complexes in vitro and render the CheW protein incapable of mediating chemotaxis in vivo file:PSEPK/PP_4332/PP_4332-uniprot.txt DR PANTHER; PTHR22617:SF23; CHEMOTAXIS PROTEIN CHEW; 1. |
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Download this section (compressed HTML)Q: Are PP_4332 and the adjacent CheW-domain protein PP_4333 redundant couplers in the flagellar array, or does PP_4333 serve a distinct role (e.g. a CheW-like scaffold for a subset of receptors)?
Experiment: Make single and double in-frame deletions of PP_4332 and PP_4333, assay chemotaxis (capillary and soft-agar) and polar chemoreceptor array formation (fluorescent CheA or CheY fusions), and test complementation by each paralogue.
Hypothesis: PP_4332 is the principal CheW required for flagellar chemotaxis in KT2440.
Type: genetics and cell imaging
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