Septin-type guanine nucleotide-binding (G) domain (IPR030379)

Short name: G_SEPTIN_dom

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.

Septins are a family of eukaryotic cytoskeletal proteins conserved from yeasts to humans. The septin family belongs to the guanosine-triphosphate (GTP)ase superclass of P-loop nucleoside triphosphate (NTP)ases. Septins participate in diverse cellular functions including cytokinesis, vesicle trafficking, vesicle fusion, axonal guidance and migration, diffusion barrier, scaffolds, pathogenesis and others. Septin monomers form homo- and hetero-oligomeric complexes that assemble into filaments. Structurally all septins have a GTP-binding domain flanked by N- and C-terminal regions of variable length. The GTP-binding domain is the most highly conserved and is characterised by the presence of three of the five classical GTP-binding motifs. The G1 motif (or Walker A box, GxxxxGKS/T) forms the P-loop, which interacts directly with the nucleotide, whereas the G3 (DxxG) and G4 (xKxD) motifs are respectively essential for Mg(2+) binding and for conferring GTP binding specificity over other nucleotides. The basic structure of the septin-type G domain closely resembles the canonical G domain exemplified by Ras, with six beta-strands and five alpha-helices. A unique feature of the septin-type G domain is the presence of four additional elements compared to Ras. These are the helix alpha5' between alpha4 and beta6, the two antiparallel strands beta7 and beta8, and the alpha6 C-terminal helix that points away from the G domain at a 90deg angle relative to the axis of interaction between subunits [PMID: 11916378, PMID: 16009555, PMID: 17637674, PMID: 23163726, PMID: 24367716].

This entry represents the septin-type G domain.

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