CheY (PP_4340) is the chemotaxis response regulator of Pseudomonas putida KT2440. It is a small (124 aa), single-domain receiver-type response regulator of the CheY/CheY-like superfamily, consisting essentially of a single REC (response regulatory) domain with a conserved phosphoaccepting aspartate (Asp52 in this protein) and a Mg2+ cofactor required for phosphochemistry. In the bacterial chemotaxis two-component signaling pathway, chemoreceptors regulate the histidine kinase CheA, which autophosphorylates and transfers the phosphoryl group to the active-site aspartate of CheY. Phosphorylated CheY (CheY-P) diffuses through the cytoplasm to the flagellar motor, where it binds the C-ring switch components (FliM/FliN) at the cytoplasmic face of the motor, shifting the rotational bias toward clockwise rotation and thereby causing cell tumbling and reorientation. The dephosphorylated state is restored by CheY-P dephosphorylation (by CheZ in canonical systems), giving the signal its transient, rapidly resettable character. Functionally, CheY acts as the diffusible output element of the chemosensory signal transduction system, converting receptor/kinase activity into changes in flagellar motor behavior and hence directed motility (chemotaxis).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000160 phosphorelay signal transduction system | IEA GO_REF:0000002 | ACCEPT | Summary: CheY is the response regulator (receiver domain) of the chemotaxis two-component/phosphorelay signaling system; it accepts a phosphoryl group from the histidine kinase CheA. This term correctly captures the core signaling role and is well supported by the conserved REC domain (IPR001789) and the conserved phosphoaccepting aspartate. Reason: Directly reflects the central, well-established function of CheY as the response-regulator output of the chemotaxis phosphorelay. The InterPro-based IEA mapping is biologically appropriate and consistent with the domain architecture and with KT2440-specific evidence that CheY (PP_4340) is phosphorylated by CheA (PP_4338). Supporting Evidence: file:PSEPK/cheY/cheY-deep-research-falcon.md Deep research synthesizes KT2440-specific and general chemotaxis evidence that CheY (PP_4340) is a chemosensory response regulator activated by phosphotransfer from the histidine kinase CheA (PP_4338), the defining step of the chemotaxis phosphorelay. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: CheY is a soluble, diffusible cytoplasmic response regulator that shuttles between the receptor-associated CheA kinase complex and the cytoplasmic C-ring of the flagellar motor. A cytoplasmic localization is consistent with the receiver-domain-only architecture (no signal peptide or transmembrane segments) and with the established mechanism of CheY action. Reason: Cytoplasmic localization is well supported for single-domain CheY response regulators and matches the UniProt subcellular location mapping. Although the action occurs at the motor, the protein itself is a freely diffusible cytoplasmic component. |
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Download this section (compressed HTML)Q: Does deletion of PP_4340 (cheY) in P. putida KT2440 produce the expected smooth-swimming (non-tumbling) chemotaxis-defective phenotype, and which of the multiple KT2440 chemosensory pathways does it serve?
Q: Which flagellar switch components (FliM/FliN/FliG) does P. putida CheY-P engage, and is the binding interface conserved relative to the E. coli paradigm?
Experiment: Construct a PP_4340 deletion mutant and assess swimming/tumbling behavior and chemotaxis toward defined attractants to confirm the predicted role in motor switching.
Experiment: Reconstitute CheA-CheY phosphotransfer in vitro with KT2440 proteins and measure phosphorylation kinetics and Mg2+ dependence at the active-site aspartate (Asp52).
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