Inner-membrane two-component system sensor histidine kinase CusS/CzcS (VPARA_44940; 443 aa) in Variovorax paradoxus TBEA6, encoded in a bicistronic operon with the response regulator czcR (VPARA_44930) immediately downstream of the czcA3-czcB-czcC-czcI heavy-metal efflux locus (VPARA_44890-VPARA_44920). Comprises two transmembrane helices (TM1 residues 21-41 and TM2 preceding the HAMP domain) flanking a periplasmic heavy-metal-sensing domain, a cytoplasmic HAMP signal-transducing linker (residues 169-222; PROSITE:PS50885), and a C-terminal histidine kinase domain (residues 230-443; PROSITE:PS50109) that undergoes ATP-dependent autophosphorylation at His-233 and transfers the phosphoryl group to CzcR (Asp-51) in response to periplasmic Zn2+, Cd2+, and Co2+.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000155 phosphorelay sensor kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: CusS (CzcS; VPARA_44940) is the transmembrane two-component sensor histidine kinase partner of CzcR (VPARA_44930), containing a HAMP domain (residues 169-222) and a HisKA/HATPase_c histidine kinase domain (residues 230-443; His-233). Reason: Directly supported by the histidine kinase domain architecture (PROSITE:PS50109, InterPro:IPR003660, InterPro:IPR003661, InterPro:IPR006290), conserved His-233 phosphoacceptor residue, and homology to Cupriavidus metallidurans CH34 CzcS (PMID:10198000). Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" FT MOD_RES 233 FT /note="Phosphohistidine; by autocatalysis" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00107" |
| GO:0000160 phosphorelay signal transduction system | IEA GO_REF:0000120 | ACCEPT | Summary: CusS functions with CzcR (VPARA_44930) in a two-component phosphorelay signal transduction system that senses periplasmic heavy metals and activates czcCBA transcription. Reason: Supported by sensor histidine kinase domain architecture (InterPro:IPR006290, NCBIfam:TIGR01386) and co-operonic organization with czcR (VPARA_44930) downstream of czcCBA-czcI (PMID:10198000). Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt DR NCBIfam; TIGR01386; cztS_silS_copS; 1. PMID:10198000 Experiments on (i) growth of these strains in liquid culture containing 5 mM Zn2+, (ii) induction of the beta-galactosidase in the reporter strains by zinc, cobalt, and cadmium, and (iii) cDNA analysis of czcCBA mRNA synthesis under inducing and noninducing conditions showed that the CzcRS two-component regulatory system is involved in Czc regulation. |
| GO:0004673 protein histidine kinase activity | IEA GO_REF:0000120 | TOO GENERAL | Summary: Direct parent term of GO:0000155 (phosphorelay sensor kinase activity), which is already accepted on this gene. Reason: True of CusS, but uninformative because the more specific child term GO:0000155 (phosphorelay sensor kinase activity) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" |
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: CusS is an integral inner-membrane (bacterial plasma membrane) sensor kinase anchored by transmembrane helices flanking its periplasmic sensor domain. Reason: Directly supported by the transmembrane helix feature (residues 21-41) and HAMP juxtamembrane linker (residues 169-222) characteristic of bacterial inner-membrane two-component sensor kinases. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT TRANSMEM 21..41 FT /note="Helical" FT /evidence="ECO:0000256|RuleBase:RU364088" |
| GO:0007165 signal transduction | IEA GO_REF:0000002 | TOO GENERAL | Summary: Ancestor term of GO:0000160 (phosphorelay signal transduction system), which is already accepted on this gene. Reason: True but uninformative because the more specific descendant term GO:0000160 (phosphorelay signal transduction system) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt DR NCBIfam; TIGR01386; cztS_silS_copS; 1. |
| GO:0016020 membrane | IEA GO_REF:0000002 | TOO GENERAL | Summary: Ancestor term of GO:0005886 (plasma membrane), which is already accepted on this gene. Reason: True but uninformative because the more specific descendant term GO:0005886 (plasma membrane) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT TRANSMEM 21..41 FT /note="Helical" FT /evidence="ECO:0000256|RuleBase:RU364088" |
| GO:0016301 kinase activity | IEA GO_REF:0000104 | TOO GENERAL | Summary: Ancestor term of GO:0000155 (phosphorelay sensor kinase activity), which is already accepted on this gene. Reason: True but uninformative because the more specific descendant term GO:0000155 (phosphorelay sensor kinase activity) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" |
| GO:0016740 transferase activity | IEA GO_REF:0000104 | TOO GENERAL | Summary: Broad enzyme class parent of GO:0000155 (phosphorelay sensor kinase activity), which is already accepted on this gene. Reason: True but uninformative because the more specific descendant term GO:0000155 (phosphorelay sensor kinase activity) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" |
| GO:0016772 transferase activity, transferring phosphorus-containing groups | IEA GO_REF:0000002 | TOO GENERAL | Summary: Ancestor term of GO:0000155 (phosphorelay sensor kinase activity), which is already accepted on this gene. Reason: True but uninformative because the more specific descendant term GO:0000155 (phosphorelay sensor kinase activity) is already asserted and accepted in this review. Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" |
| GO:0005524 ATP binding | IC file:VARPD/cusS/cusS-uniprot.txt | NEW | Summary: CusS contains a C-terminal HATPase_c ATP-binding catalytic domain within its histidine kinase domain (residues 230-443; Pfam:PF02518, InterPro:IPR003594). Reason: Histidine kinase autophosphorylation at His-233 requires ATP binding by the Bergerat-fold HATPase_c domain (Pfam:PF02518; PROSITE:PS50109). Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT DOMAIN 230..443 FT /note="Histidine kinase" FT /evidence="ECO:0000259|PROSITE:PS50109" FT MOD_RES 233 FT /note="Phosphohistidine; by autocatalysis" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00107" |
| GO:0046777 protein autophosphorylation | IC file:VARPD/cusS/cusS-uniprot.txt | NEW | Summary: CusS undergoes autocatalytic phosphorylation at His-233 upon periplasmic heavy-metal sensing. Reason: UniProt PROSITE-ProRule:PRU00107 annotates His-233 as a phosphohistidine formed by autocatalysis within the histidine kinase domain (residues 230-443). Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt FT MOD_RES 233 FT /note="Phosphohistidine; by autocatalysis" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00107" |
| GO:0010043 response to zinc ion | ISS PMID:10198000 Transcriptional organization of the czc heavy-metal homeosta... | NEW | Summary: CusS (CzcS; VPARA_44940) is the heavy-metal-sensing histidine kinase of the VPARA_44890-VPARA_44940 czc island that initiates the transcriptional response to periplasmic Zn2+, Cd2+, and Co2+. Reason: Although automatically named cusS by homology to the Cu+/Ag+/Zn2+/Cd2+ sensor family (NCBIfam:TIGR01386 cztS_silS_copS), VPARA_44940 is encoded immediately downstream of czcA3-czcB-czcC-czcI-czcR (VPARA_44890-VPARA_44930) as the CzcS sensor kinase of the czc Zn2+/Cd2+/Co2+ resistance determinant (PMID:10198000). Supporting Evidence: file:VARPD/cusS/cusS-uniprot.txt DR NCBIfam; TIGR01386; cztS_silS_copS; 1. PMID:10198000 Experiments on (i) growth of these strains in liquid culture containing 5 mM Zn2+, (ii) induction of the beta-galactosidase in the reporter strains by zinc, cobalt, and cadmium, and (iii) cDNA analysis of czcCBA mRNA synthesis under inducing and noninducing conditions showed that the CzcRS two-component regulatory system is involved in Czc regulation. |
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Download this section (compressed HTML)Q: Which histidine and acidic residues in the periplasmic sensor loop (residues 42-145) of VPARA_44940 directly coordinate Zn2+, Cd2+, and Co2+, and does periplasmic CzcI (VPARA_44920) physically interact with this sensor domain to raise the metal threshold for CusS autophosphorylation?
Experiment: Express and purify the isolated periplasmic sensor domain of VPARA_44940 (residues 42-145) and determine its binding affinities (Kd) for Zn2+, Cd2+, Co2+, Cu2+, and Ni2+ by isothermal titration calorimetry and intrinsic tryptophan fluorescence.
Hypothesis: Consistent with its genomic context in the czcNICBARS island, the periplasmic sensor domain of VPARA_44940 selectively binds divalent Zn2+, Cd2+, and Co2+ rather than monovalent Cu+/Ag+.
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