GAIP and RGS4 are GTPase- activating proteins for the Gi subfamily of G protein alpha subunits.
A novel class of regulators of G protein signaling ( RGS) proteins has been identified recently. Genetic evidence suggests that RGS proteins inhibit G protein-mediated signaling at the level of the receptor-G protein interaction or the G protein alpha subunit itself. We have found that two RGS family members, GAIP and RGS4, are GTPase-activating proteins (GAPs), accelerating the rate of GTP hydrolysis by Gi alpha 1 at least 40-fold. All Gi subfamily members assayed were substrates for these GAPs; Gs alpha was not. RGS4 activates the GTPase activity of certain Gi alpha 1 mutants (e.g., R178C), but not others (e.g., Q204L). The GAP activity of RGS proteins is consistent with their proposed role as negative regulators of G protein-mediated signaling.[1]References
- GAIP and RGS4 are GTPase-activating proteins for the Gi subfamily of G protein alpha subunits. Berman, D.M., Wilkie, T.M., Gilman, A.G. Cell (1996) [Pubmed]
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