This domain is found in HypB, a hydrogenase expression / formation protein, and UreG a urease accessory protein. Both these proteins contain a P-loop nucleotide binding motif [2,3]. HypB has GTPase activity and is a guanine nucleotide binding protein [3]. It is not known whether UreG binds GTP or some other nucleotide. Both enzymes are involved in nickel binding. HypB can store nickel and is required for nickel dependent hydrogenase expression [1]. UreG is required for functional incorporation of the urease nickel metallocenter.[4] GTP hydrolysis may required by these proteins for nickel incorporation into other nickel proteins [1]. This family of domains also contains P47K (Swiss:P31521), a Pseudomonas chlororaphis protein needed for nitrile hydratase expression, and the cobW gene product (Swiss:P29937), which may be involved in cobalamin biosynthesis in Pseudomonas denitrificans [5].

1: The HypB protein from Bradyrhizobium japonicum can store nickel and is required for the nickel-dependent transcriptional regulation of hydrogenase. Olson JW, Fu C, Maier RJ; Mol Microbiol 1997;24:119-128. PMID:9140970

2: Characterization of UreG, identification of a UreD-UreF-UreG complex, and evidence suggesting that a nucleotide-binding site in UreG is required for in vivo metallocenter assembly of Klebsiella aerogenes urease. Moncrief MB, Hausinger RP; J Bacteriol 1997;179:4081-4086. PMID:9209019

3: The product of the hypB gene, which is required for nickel incorporation into hydrogenases, is a novel guanine nucleotide-binding protein. Maier T, Jacobi A, Sauter M, Bock A; J Bacteriol 1993;175:630-635. PMID:8423137

4: Klebsiella aerogenes urease gene cluster: sequence of ureD and demonstration that four accessory genes (ureD, ureE, ureF, and ureG) are involved in nickel metallocenter biosynthesis. Lee MH, Mulrooney SB, Renner MJ, Markowicz Y, Hausinger RP; J Bacteriol 1992;174:4324-4330. PMID:1624427

5: Nucleotide sequence and genetic analysis of a 13.1-kilobase-pair Pseudomonas denitrificans DNA fragment containing five cob genes and identification of structural genes encoding Cob(I)alamin adenosyltransferase, cobyric acid synthase, and bifunctional cob Crouzet J, Levy-Schil S, Cameron B, Cauchois L, Rigault S, Rouyez MC, Blanche F, Debussche L, Thibaut D; J Bacteriol 1991;173:6074-6087. PMID:1655697