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RGS Domain

No ImageThe RGS domain is composed of nine alpha helices, which form a right-handed anti-parallel four helix bundle (a4-7) and a terminal bundle (a1-3, a8-9) which contains the N- and C-termini of the domain. The loop between a3-4, the loop between a5-6, the end of a7 and the start of a8 form an interaction surface between RGS4 and Gai. All RGS domains have been found to share a highly similar tertiary structure even amongst members with a low identity of amino acids. Interestingly, the structure of the RGS domain is quite different than that of the GAP domains for the monomeric G proteins such as p120 RhoGAP.

Structure reference:
Tesmer, J.J. et al. (1997) Cell. 89(2): 251-261. PDB: 1AGR.

Domain binding and function:
The RGS (Regulator of G protein Signaling) domain has been found in over 20 proteins in humans and is typically about 120 amino acids in length. RGS domains act allosterically by stabilizing the transition intermediate of the GTP binding pocket of the alpha subunit of heterotrimeric G proteins. This results in the acceleration of the intrinsic GTPase activity of that alpha subunit. The discovery of the RGS domain therefore answered the longstanding question of why the intrinsic rate of hydrolysis of many heterotrimeric G proteins was often slower than the apparent cycling time for a signaling process requiring that G protein. Heterotrimeric G proteins transmit signaling from seven transmembrane receptors, which, in turn, are activated by many important agonists such as hormones, neurotransmitters, light and odorants. Proteins that encode RGS domains also modulate such signaling events as they control the time of transmission of each of these agonists.
Examples of Proteins: 
RGS Domain Proteins
Binding Partners
RGS-4 GAi, GAq
p115 RhoGEF GA12, GA13

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