InterPro domain: IPR003495

This domain is found in HypB, a hydrogenase expression/formation protein, and urease accessory protein UreG. Both these proteins contain a P-loop nucleotide binding motif [ 1 , 2 ]. HypB has GTPase activity and is a guanine nucleotide binding protein [ 3 ]. UreG is a GTPase in charge of nucleotide hydrolysis required for activation of the urease enzyme [ 3 ]. Both GTPases are involved in nickel binding. HypB can store nickel and is required for nickel dependent hydrogenase expression [ 4 ]. UreG is required for functional incorporation of the urease nickel metallocentre [ 5 ]. GTP hydrolysis may required by these proteins for nickel incorporation into other nickel proteins [ 6 ].

Other proteins containing this domain include P47K ( P31521 ), a Pseudomonas chlororaphis protein needed for nitrile hydratase expression, CobW ( P29937 ), which may be involved in cobalamin biosynthesis in Pseudomonas denitrificans [ 6 ], and YjiA [ 7 ]. Both CobW and YjiA are members of the metal homeostasis-associated COG0523 family of GTPases [ 8 ].

1. 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. J. Bacteriol. 179, 4081-6
2. The product of the hypB gene, which is required for nickel incorporation into hydrogenases, is a novel guanine nucleotide-binding protein. J. Bacteriol. 175, 630-5
3. Intrinsic disorder and metal binding in UreG proteins from Archae hyperthermophiles: GTPase enzymes involved in the activation of Ni(II) dependent urease. J. Biol. Inorg. Chem. 20, 739-55
4. The HypB protein from Bradyrhizobium japonicum can store nickel and is required for the nickel-dependent transcriptional regulation of hydrogenase. Mol. Microbiol. 24, 119-28
5. 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. J. Bacteriol. 174, 4324-30
6. 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 cobinamide kinase-cobinamide phosphate guanylyltransferase. J. Bacteriol. 173, 6074-87
7. Crystal structure of the Escherichia coli YjiA protein suggests a GTP-dependent regulatory function. Proteins 54, 371-4
8. Metal binding properties of Escherichia coli YjiA, a member of the metal homeostasis-associated COG0523 family of GTPases. Biochemistry 52, 1788-1801