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Date: 26 March 1999

Journal: Journal of Biological Chemistry Volume 274, Issue 13, 26 March 1999, Pages 8770-8778 , Doi: 10.1074/jbc.274.13.8770

1999 | The α-helical domain of Gα(t) determines specific interaction with regulator of G protein signaling 9…

Skiba, N.P.a, Yang, C.-S.b, Huang, T.a, Bae, H.a, Hamm, H.E.ac

첨부파일

Abstract

RGS proteins (regulators of G protein signaling) are potent accelerators of the intrinsic GTPase activity of G protein α subunits (GAPs), thus controlling the response kinetics of a variety of cell signaling processes. Most RGS domains that have been studied have relatively little GTPase activating specificity especially for G proteins within the G(i) subfamily. Retinal RGS9 is unique in its ability to act synergistically with a downstream effector cGMP phosphodiesterase to stimulate the GTPase activity of the α subunit of transducin, Gα(t). Here we report another unique property of RGS9: high specificity for Gα(t). The core (RGS) domain of RGS9 (RGS9) stimulates Gα(t) GTPase activity by 10-fold and Gα(i1) GTPase activity by only 2-fold at a concentration of 10 μM. Using chimeric Gα(t)/Gα(i1) subunits we demonstrated that the α-helical domain of Gα(t) imparts this specificity. The functional effects of RGS9 were well correlated with its affinity for activated Gα subunits as measured by a change in fluorescence of a mutant Gα(t) (Chi6b) selectively labeled at Cys-210. K(d) values for RGS9 complexes with Gα(t) and Gα(i1) calculated from the direct binding and competition experiments were 185 nM and 2 μM, respectively. The γ subunit of phosphodiesterase increases the GAP activity of RGS9. We demonstrate that this is because of the ability of Pγ to increase the affinity of RGS9 for Gα(t). A distinct, nonoverlapping pattern of RGS and Pγ interaction with Gα(t) suggests a unique mechanism of effector-mediated GAP function of the RGS9.


Indexed keywords

EMTREE drug terms: guanine nucleotide binding protein; guanosine triphosphatase; phosphodiesterase

EMTREE medical terms: animal cell; article; binding affinity; chimera; enzyme activity; enzyme binding; enzyme specificity; enzyme structure; nonhuman; priority journal; protein domain; protein expression; protein interaction; protein purification; rat

MeSH: 3',5'-Cyclic-GMP Phosphodiesterase; Eye Proteins; Fluorescence; GTP Phosphohydrolases; GTP-Binding Proteins; GTPase-Activating Proteins; Kinetics; Models, Molecular; Protein Binding; Protein Structure, Secondary; Proteins; Transducin
Medline is the source for the MeSH terms of this document.

Species Index: Animalia


Chemicals and CAS Registry Numbers: 3',5'-Cyclic-GMP Phosphodiesterase, EC 3.1.4.35; Eye Proteins; GTP Phosphohydrolases, EC 3.6.1.-; GTP-Binding Proteins, EC 3.6.1.-; GTPase-Activating Proteins; Proteins; Transducin, EC 3.6.1.-


ISSN: 00219258 CODEN: JBCHASource Type: Journal Original language: English
DOI: 10.1074/jbc.274.13.8770 PubMed ID: 10085118 Document Type: Article
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