Regulator of G protein signalling
|Regulator of G-Protein Signaling Domain|
Structures of active conformations of Gi alpha 1.
RGS proteins are multi-functional, GTPase-accelerating proteins that promote GTP hydrolysis by the alpha subunit of heterotrimeric G proteins, thereby inactivating the G protein and rapidly switching off G protein-coupled receptor signaling pathways. Upon activation by GPCRs, heterotrimeric G proteins exchange GDP for GTP, are released from the receptor, and dissociate into free, active GTP-bound alpha subunit and beta-gamma dimer, both of which activate downstream effectors. The response is terminated upon GTP hydrolysis by the alpha subunit (IPR001019), which can then bind the beta-gamma dimer (IPR001632 IPR001770) and the receptor. RGS proteins markedly reduce the lifespan of GTP-bound alpha subunits by stabilising the G protein transition state.
All RGS proteins contain an RGS-box (or RGS domain), which is required for activity. Some small RGS proteins such as RGS1 and RGS4 are little more than an RGS domain, while others also contain additional domains that confer further functionality.
RGS domains can be found within the same protein in combination with a variety of other domains, including: DEP for membrane targeting (IPR000591), PDZ for binding to GPCRs (IPR001478), PTB for phosphotyrosine-binding (IPR006020), RBD for Ras-binding (IPR003116), GoLoco for guanine nucleotide inhibitor activity (IPR003109), PX for phosphoinositide-binding (IPR001683), PXA that is associated with PX (IPR003114), PH for phosphatidylinositol-binding (IPR001849), and GGL (G protein gamma subunit-like) for binding G protein beta subunits (IPR001770 Those RGS proteins that contain GGL domains can interact with G protein beta subunits to form novel dimers that prevent G protein gamma subunit binding and G protein alpha subunit association, thereby preventing heterotrimer formation.
Human proteins containing this domain include:
- ADRBK1, ADRBK2, AXIN1, AXIN2
- GRK1, GRK4, GRK5, GRK6, GRK7,
- RGS1, RGS2, RGS3, RGS4, RGS5, RGS6, RGS7, RGS8, RGS9, RGS10, RGS11, RGS12, RGS13, RGS14, RGS16, RGS17, RGS18, RGS19, RGS20, RGS21
GTP-binding protein regulators:
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- Tesmer, JJ; Berman, DM; Gilman, AG; Sprang, SR (1997). "Structure of RGS4 bound to AlF4--activated G(i alpha1): Stabilization of the transition state for GTP hydrolysis". Cell 89 (2): 251–61. doi:10.1016/s0092-8674(00)80204-4. PMID 9108480.
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- Berman DM, Wilkie TM, Gilman AG (August 1996). "GAIP and RGS4 are GTPase-activating proteins for the Gi subfamily of G protein alpha subunits". Cell 86 (3): 445–52. doi:10.1016/S0092-8674(00)80117-8. PMID 8756726.
- De Vries L, Mousli M, Wurmser A, Farquhar MG (December 1995). "GAIP, a protein that specifically interacts with the trimeric G protein G alpha i3, is a member of a protein family with a highly conserved core domain". Proc. Natl. Acad. Sci. U.S.A. 92 (25): 11916–20. doi:10.1073/pnas.92.25.11916. PMC 40514. PMID 8524874.