UreB (Vapar_4242) in Variovorax paradoxus S110 is the 101-amino-acid cytoplasmic beta structural subunit (HAMAP rule MF_01954, InterPro IPR002019, Pfam PF00699) of the three-chain bacterial urease complex. Encoded immediately upstream of the catalytic alpha subunit gene ureC (Vapar_4243) on chromosome 1, UreB associates with UreA (gamma subunit, Vapar_4240) and UreC to form the (UreABC)3 trimer of heterotrimers and contributes structurally to nickel-dependent urea hydrolysis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: UreB is a cytoplasmic subunit of the soluble UreABC urease complex. Reason: C5CXZ9 (Vapar_4242) is a soluble 101-residue protein that assembles with UreA and UreC in the bacterial cytoplasm (HAMAP rule MF_01954). Supporting Evidence: UniProtKB:C5CXZ9 CC -!- SUBCELLULAR LOCATION: Cytoplasm {ECO:0000255|HAMAP-Rule:MF_01954}. |
| GO:0009039 urease activity | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: UreB contributes structurally to the heteromeric urease complex but does not independently catalyze urea hydrolysis. Reason: UreB (Vapar_4242) is the non-catalytic beta structural chain of the (UreABC)3 complex; the binickel active site resides exclusively in the alpha subunit UreC (Vapar_4243, C5CY00; PMID:8718850). Asserting that UreB independently enables urease activity over-annotates an individual structural subunit; instead, UreB enables structural molecule activity (GO:0005198) and contributes_to urease activity (GO:0009039) within the assembled complex. Supporting Evidence: PMID:8718850 Urease from Klebsiella aerogenes [Jabri et al. (1995) Science 268, 998-1004] is an (alpha beta gamma)3 trimer with each alpha-subunit having an (alpha beta)8-barrel domain containing a binickel active center. |
| GO:0035550 urease complex | IEA GO_REF:0000002 | ACCEPT | Summary: UreB is the beta subunit of the heterotrimeric (UreABC)3 urease complex. Reason: C5CXZ9 belongs to the conserved urease beta subunit family (HAMAP MF_01954, InterPro IPR002019) and forms the beta chain of the (UreABC)3 urease complex (GO:0035550). Supporting Evidence: UniProtKB:C5CXZ9 CC -!- SUBUNIT: Heterotrimer of UreA (gamma), UreB (beta) and UreC (alpha) CC subunits. Three heterotrimers associate to form the active enzyme. CC {ECO:0000255|HAMAP-Rule:MF_01954}. |
| GO:0043419 urea catabolic process | IEA GO_REF:0000120 | ACCEPT | Summary: UreB is an essential structural component of the urea-hydrolyzing UreABC complex. Reason: UreB is required for assembly of the mature (UreABC)3 urease complex that directly hydrolyzes urea in the urea catabolic pathway. Supporting Evidence: UniProtKB:C5CXZ9 CC -!- PATHWAY: Nitrogen metabolism; urea degradation; CO(2) and NH(3) from CC urea (urease route): step 1/1. {ECO:0000255|HAMAP-Rule:MF_01954}. |
| GO:0005198 structural molecule activity | ISS PMID:8718850 Structures of the Klebsiella aerogenes urease apoenzyme and ... | NEW | Summary: UreB supplies structural integrity to the heteromeric (UreABC)3 urease complex. Reason: Inferred from sequence and structural similarity (ISS) to Klebsiella aerogenes UreB (PMID:8718850), where the beta chain is a non-catalytic structural subunit of the (alpha beta gamma)3 assembly. Supporting Evidence: PMID:8718850 Urease from Klebsiella aerogenes [Jabri et al. (1995) Science 268, 998-1004] is an (alpha beta gamma)3 trimer with each alpha-subunit having an (alpha beta)8-barrel domain containing a binickel active center. |
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Download this section (compressed HTML)Q: Does UreB (Vapar_4242) directly contact the UreD-UreF-UreG accessory chaperone complex during nickel metallocenter installation into UreC (Vapar_4243) in Variovorax paradoxus S110?
Experiment: Co-express Vapar_4240 (ureA) and Vapar_4243 (ureC) with and without Vapar_4242 (ureB) alongside the accessory genes and quantify apoprotein complex stability and Ni(2+)-dependent urease activation.
Hypothesis: Vapar_4242 (UreB) is required both for structural stability of the (UreABC)3 apoprotein and for productive docking of the UreDFG activation scaffold.
Type: Recombinant co-expression, native complex pull-down, and urease activation assay
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