UreE (VPARA_50940) in Variovorax paradoxus is a 200-amino-acid cytoplasmic nickel-binding metallochaperone for urease maturation (HAMAP rule MF_00822, InterPro IPR012406, Pfam PF02814/PF05194) featuring an N-terminal dimerization/chaperone domain, a C-terminal metal-binding domain, and a histidine-rich C-terminal tail (residues 148-200 containing 15 His residues). Encoded immediately upstream of ureF (VPARA_50930) in the urease gene cluster, UreE binds intracellular Ni(2+) and donates it to the UreD-UreF-UreG activation complex for installation of the dinickel active site in UreC.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: UreE is a soluble cytoplasmic nickel metallochaperone. Reason: A0A0H2LU38 (VPARA_50940) is a soluble 200-residue cytoplasmic protein (HAMAP rule MF_00822) consistent with immunogold localization of characterized bacterial UreE (PMID:8318889). Supporting Evidence: UniProtKB:A0A0H2LU38 CC -!- SUBCELLULAR LOCATION: Cytoplasm {ECO:0000256|ARBA:ARBA00004496, CC ECO:0000256|HAMAP-Rule:MF_00822}. |
| GO:0006457 protein folding | IEA GO_REF:0000002 | MODIFY | Summary: InterPro-to-GO conflates metallochaperone-mediated cofactor insertion with general protein folding; replace with protein maturation (GO:0051604). Reason: UreE is a nickel-binding metallochaperone that donates Ni(2+) for urease active-site maturation rather than folding nascent polypeptides (PMID:8318889). Following the repository-wide convention for bacterial UreE (after obsoletion of GO:0110147 protein maturation by nickel ion transfer), GO:0006457 is modified to GO:0051604 (protein maturation). Proposed replacements: protein maturation Supporting Evidence: PMID:8318889 We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein. |
| GO:0016151 nickel cation binding | IEA GO_REF:0000120 | ACCEPT | Summary: Nickel cation binding is the defining molecular function of UreE. Reason: VPARA_50940 (A0A0H2LU38) possesses the conserved UreE N-terminal (PF02814) and C-terminal (PF05194) domains plus a 15-histidine C-terminal metal-binding tail (HEHSHGGGHDHAHDHG...HDHSHGHDHGHHGHSH) characteristic of bacterial UreE nickel metallochaperones (HAMAP MF_00822; PMID:8318889). Supporting Evidence: UniProtKB:A0A0H2LU38 CC -!- FUNCTION: Involved in urease metallocenter assembly. Binds nickel. CC Probably functions as a nickel donor during metallocenter assembly. CC {ECO:0000256|HAMAP-Rule:MF_00822}. PMID:8318889 We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein. |
| GO:0019627 urea metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: Broad parent process refined to urea catabolic process (GO:0043419). Reason: UreE specifically supplies nickel to mature the urease enzyme that catalyzes urea catabolism, so the broad term urea metabolic process (GO:0019627) is refined to its specific child term urea catabolic process (GO:0043419). Proposed replacements: urea catabolic process Supporting Evidence: PMID:8318889 We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein. |
| GO:0065003 protein-containing complex assembly | IEA GO_REF:0000002 | MODIFY | Summary: UreE mediates nickel metallocenter maturation rather than polypeptide subunit assembly; replace with protein maturation (GO:0051604). Reason: The (UreABC)3 apoprotein complex assembles independently of UreE; UreE acts subsequently to donate Ni(2+) for active-site maturation (PMID:8318889). Therefore GO:0065003 is replaced by GO:0051604 (protein maturation). Proposed replacements: protein maturation Supporting Evidence: PMID:8318889 We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein. |
Loading supporting content…
Download this section (compressed HTML)Q: How many Ni(2+) ions are coordinated per dimer by the 15-histidine C-terminal extension (residues 148-200) of Variovorax paradoxus UreE (VPARA_50940)?
Experiment: Compare Ni(2+) binding stoichiometry by isothermal titration calorimetry (ITC) and in vivo urease activity between full-length VPARA_50940 and a C-terminally truncated UreE(1-147) variant across a gradient of media NiCl2 concentrations.
Hypothesis: Truncation of the C-terminal histidine-rich tail (residues 148-200) of VPARA_50940 reduces high-capacity Ni(2+) buffering and impairs urease activation under low-nickel conditions.
Type: Site-directed truncation, isothermal titration calorimetry, and urease activation assay
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)