Ras association (RalGDS/AF-6) domain
SMART accession number:SM00314
Description: RasGTP effectors (in cases of AF6, canoe and RalGDS); putative RasGTP effectors in other cases. Kalhammer et al. have shown that not all RA domains bind RasGTP. Predicted structure similar to that determined, and that of the RasGTP-binding domain of Raf kinase. Predicted RA domains in PLC210 and nore1 found to bind RasGTP. Included outliers (Grb7, Grb14, adenylyl cyclases etc.)
Interpro abstract (IPR000159):

Ras proteins are signal-transducing GTPases that cycle between inactive GDP- bound and active GTP-bound forms. Ras is a prolific signalling molecule interacting with a spectrum of effector molecules and acting through more than one signalling pathway. A domain of about 100 residues, termed RA for RalGDS/AF-6 or Ras-Associating, interacts with Ras and other small GTPases. It occurs in one or two copies in a variety of signalling molecules. It can be found associated with many other domains, such as PDZ, Dilute (DIL), GEF, myosin motor, IQ, C1, C2, protein kinase, VPS9 or sterile alpha motif (SAM) [(PUBMED:8987396), (PUBMED:11723130)].

Structurally, the RA domain of RalGDS consists of a five-stranded mixed beta- sheet interrupted by a 12 residue alpha-helix and two additional small alpha- helices. The structure of the RA domain belongs to the ubiquitin alpha/beta roll superfold and is similar to that of the RBD domain and the N-terminal third of the FERM domain [(PUBMED:9253406), (PUBMED:10334925)]. The RA domain forms a homodimer where the interdimer surface is composed of two cysteines (Cys 2 in each monomer) forming an intermolecular disulfide bond and two interacting intermolecular antiparallel beta-sheets [(PUBMED:9253406)]. The major interaction between Ras and RalGDS RA domain occurs between two antiparallel beta-strands: beta 2 of Ras and beta 2 of RA. This interaction occurs both at the backbone as well as the side chain level [(PUBMED:9628477)].

GO process:signal transduction (GO:0007165)
Family alignment:
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There are 20447 RA domains in 18300 proteins in SMART's nrdb database.

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