CheZ (PP_4339) is the chemotaxis signal-terminating phosphatase of Pseudomonas putida KT2440. It accelerates the dephosphorylation of the phosphorylated response regulator CheY (CheY-P), the diffusible output of the chemotaxis phosphorelay. By lowering CheY-P levels, CheZ resets the pathway after stimulation and sets how much phosphorylated CheY reaches the flagellar motor, tuning the balance between runs and direction changes. The protein belongs to the CheZ family (Pfam PF04344; InterPro IPR007439) of response-regulator aspartyl-phosphate phosphatases, which share a conserved DXXXQ catalytic motif and a C-terminal CheY-P binding segment. CheZ is a soluble cytoplasmic homodimer; in E. coli and other bacteria it is enriched at chemoreceptor arrays through interaction with CheA. In KT2440 the gene lies between cheY and cheA2 in a cheYZA cluster of the flagellar/chemotaxis gene region, and CheZ co-purifies with CheA from KT2440 cell extracts.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: CheZ is a CheY-P (aspartyl-phosphate) phosphatase; catalytic activity is correct but is the root of the catalytic branch. Reason: True but general. The specific activity supported for the CheZ family is dephosphorylation of a phosphorylated protein (CheY-P), which is GO:0004721 phosphoprotein phosphatase activity ("a phosphoprotein + H2O = a protein + phosphate"), an is_a descendant of catalytic activity and the module-level activity of CheZ. Proposed replacements: phosphoprotein phosphatase activity Supporting Evidence: file:PSEPK/cheZ/cheZ-uniprot.txt FUNCTION: Plays an important role in bacterial chemotaxis signal transduction pathway by accelerating the dephosphorylation of phosphorylated CheY (CheY-P). file:PSEPK/cheZ/cheZ-uniprot.txt SITE 181 /note="Enhances dephosphorylation of CheY-P" file:PSEPK/cheZ/cheZ-deep-research-falcon.md CheZ-family proteins share a conserved **DXXXQ** catalytic motif. Multiple experimental systems demonstrate that the corresponding Asp/Gln residues are required for phosphatase activity |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: CheZ is a soluble cytoplasmic phosphatase acting on diffusible CheY-P. Reason: The curated UniProt subcellular location (by similarity) is cytoplasm, and no KT2440 localization data exist that would support a more specific term such as a cell pole or receptor array; cytoplasm is as precise as the evidence for this protein allows. Supporting Evidence: file:PSEPK/cheZ/cheZ-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm file:PSEPK/cheZ/cheZ-deep-research-falcon.md For KT2440 CheZ (Q88EW3), the most defensible annotation is therefore **cytoplasmic** with **likely enrichment at chemotaxis/flagellar signaling regions** |
| GO:0009288 bacterial-type flagellum | IEA GO_REF:0000002 | REMOVE | Summary: CheZ is a cytoplasmic CheY-P phosphatase, not a component of the flagellum. Reason: The row comes from the InterPro2GO mapping of IPR007439 (Chemotax_Pase_CheZ) to GO:0009288. CheZ-family phosphatases are soluble and, where localized, sit at chemoreceptor arrays (E. coli, via CheA-short) or at a cell pole through other partners (H. pylori ChePep); they are not part of the filament, hook or basal body. The mapping is wrong for the whole family, consistent with the E. coli CheZ review. Supporting Evidence: file:PSEPK/cheZ/cheZ-deep-research-falcon.md In *E. coli*, CheZ localizes to the chemotaxis signaling cluster via interaction with CheA/CheA-short (CheAs). file:PSEPK/cheZ/cheZ-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0050920 regulation of chemotaxis | IEA GO_REF:0000002 | ACCEPT | Summary: CheZ regulates chemotaxis by dephosphorylating CheY-P to terminate and reset the signaling output. Reason: Controlling the level of CheY-P, and with it the rate of direction changes, is the core biological role of CheZ. In KT2440 CheZ is encoded in the swimming chemotaxis cluster and the genome analysis states that CheY activity is regulated by CheZ. Supporting Evidence: file:PSEPK/cheZ/cheZ-deep-research-falcon.md In KT2440, this canonical relationship is explicitly stated: **“The activity of the transducer CheY is regulated by the phosphatase CheZ.”** file:PSEPK/cheZ/cheZ-uniprot.txt FUNCTION: Plays an important role in bacterial chemotaxis signal transduction pathway by accelerating the dephosphorylation of phosphorylated CheY (CheY-P). PMID:40197389 the response regulator CheY and the phosphatase CheZ (two proteins known to be associated with CheA) also showed high Log2(fold change) values |
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Download this section (compressed HTML)Q: Does KT2440 CheZ localize to polar chemoreceptor arrays, and if so through which partner, given that P. putida has no CheA-short?
Q: Which of the KT2440 CheY paralogs are substrates of CheZ (PP_4339)?
Experiment: Construct a PP_4339 deletion and measure swimming reversal frequency, soft-agar spreading and capillary chemotaxis, with complementation by wild-type and DXXXQ-motif mutant alleles.
Hypothesis: Loss of CheZ phosphatase activity raises CheY-P and causes a hyper-reversal, chemotaxis-defective phenotype.
Type: mutant phenotyping
Experiment: Measure CheY-P dephosphorylation rates with purified KT2440 CheZ and each CheY paralog.
Hypothesis: CheZ selectively accelerates dephosphorylation of the chemotaxis CheY (PP_4340).
Type: in vitro phosphatase assay
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