OBG-type guanine nucleotide-binding (G) domain (IPR031167)

Short name: G_OBG

Overlapping homologous superfamilies

Domain relationships


The P-loop guanosine triphosphatases (GTPases) control a multitude of biological processes, ranging from cell division, cell cycling, and signal transduction, to ribosome assembly and protein synthesis. GTPases exert their control by interchanging between an inactive GDP-bound state and an active GTP-bound state, thereby acting as molecular switches. The common denominator of GTPases is the highly conserved guanine nucleotide-binding (G) domain that is responsible for binding and hydrolysis of guanine nucleotides.

Within the translation factor-related (TRAFAC) class of P-loop GTPases, the OBG family comprises a group of high-molecular mass GTPases conserved from bacteria to eukaryotes. The OBG family consists of [PMID: 11916378]:

  • Obg from bacteria and eukaryotes [PMID: 12429099, PMID: 15019792].
  • DRG from eukaryotes and archaea. DRG proteins may regulate fundamental cellular processes through RNA binding [PMID: 14644502].
  • Nog1 from eukaryotes and archaea. It is involved in the assembly of the large ribosomal subunit.
  • Yyaf/YchF from bacteria and eukaryotes. It consists of a central G domain, flanked by a coiled-coil domain and a TGS (ThrRS, GTPase, SpoT) domain. Members of this subfamily bind and hydolyze ATP more efficiently than GTP [PMID: 12837776, PMID: 17430889].
  • Ygr210 from archaea and fungi.

The OBG-type G domain has a mononucleotide binding fold typical for the P-loop NTPases. A six-stranded mostly parallel beta-sheet is flanked by alpha-helices on both sides. The OBG-type G domain contains five characteristic sequence motifs, termed G1-G5, involved in nucleotide binding and hydrolysis. The G1/Walker A motif (GXXXXGK(S/T)), also referred to as P- loop, helps to position the triphosphate moiety of the bound nucleotide. The G2 (X(T/S)X) and G3/Walker B (hhhDXXG) motifs are involved in the coordination of a Mg(2)+ ion that is required for nucleotide binding and hydrolysis. Specificity in nucleotide binding is conferred by the G4 motif, which has a (N/T)KXD signature in guanine nucleotide binding P-loop NTPases. The G5 motif ((T/G)(C/S)A) supports guanine base recognition [PMID: 12429099, PMID: 15019792, PMID: 12837776, PMID: 17430889].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0005525 GTP binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles