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The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9.

Publication ,  Journal Article
Skiba, NP; Yang, CS; Huang, T; Bae, H; Hamm, HE
Published in: J Biol Chem
March 26, 1999

RGS proteins (regulators of G protein signaling) are potent accelerators of the intrinsic GTPase activity of G protein alpha 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 Gi subfamily. Retinal RGS9 is unique in its ability to act synergistically with a downstream effector cGMP phosphodiesterase to stimulate the GTPase activity of the alpha subunit of transducin, Galphat. Here we report another unique property of RGS9: high specificity for Galphat. The core (RGS) domain of RGS9 (RGS9) stimulates Galphat GTPase activity by 10-fold and Galphai1 GTPase activity by only 2-fold at a concentration of 10 microM. Using chimeric Galphat/Galphai1 subunits we demonstrated that the alpha-helical domain of Galphat imparts this specificity. The functional effects of RGS9 were well correlated with its affinity for activated Galpha subunits as measured by a change in fluorescence of a mutant Galphat (Chi6b) selectively labeled at Cys-210. Kd values for RGS9 complexes with Galphat and Galphai1 calculated from the direct binding and competition experiments were 185 nM and 2 microM, respectively. The gamma subunit of phosphodiesterase increases the GAP activity of RGS9. We demonstrate that this is because of the ability of Pgamma to increase the affinity of RGS9 for Galphat. A distinct, nonoverlapping pattern of RGS and Pgamma interaction with Galphat suggests a unique mechanism of effector-mediated GAP function of the RGS9.

Duke Scholars

Published In

J Biol Chem

DOI

ISSN

0021-9258

Publication Date

March 26, 1999

Volume

274

Issue

13

Start / End Page

8770 / 8778

Location

United States

Related Subject Headings

  • Transducin
  • Proteins
  • Protein Structure, Secondary
  • Protein Binding
  • Models, Molecular
  • Kinetics
  • GTPase-Activating Proteins
  • GTP-Binding Proteins
  • GTP Phosphohydrolases
  • Fluorescence
 

Citation

APA
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MLA
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Skiba, N. P., Yang, C. S., Huang, T., Bae, H., & Hamm, H. E. (1999). The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9. J Biol Chem, 274(13), 8770–8778. https://doi.org/10.1074/jbc.274.13.8770
Skiba, N. P., C. S. Yang, T. Huang, H. Bae, and H. E. Hamm. “The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9.J Biol Chem 274, no. 13 (March 26, 1999): 8770–78. https://doi.org/10.1074/jbc.274.13.8770.
Skiba NP, Yang CS, Huang T, Bae H, Hamm HE. The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9. J Biol Chem. 1999 Mar 26;274(13):8770–8.
Skiba, N. P., et al. “The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9.J Biol Chem, vol. 274, no. 13, Mar. 1999, pp. 8770–78. Pubmed, doi:10.1074/jbc.274.13.8770.
Skiba NP, Yang CS, Huang T, Bae H, Hamm HE. The alpha-helical domain of Galphat determines specific interaction with regulator of G protein signaling 9. J Biol Chem. 1999 Mar 26;274(13):8770–8778.

Published In

J Biol Chem

DOI

ISSN

0021-9258

Publication Date

March 26, 1999

Volume

274

Issue

13

Start / End Page

8770 / 8778

Location

United States

Related Subject Headings

  • Transducin
  • Proteins
  • Protein Structure, Secondary
  • Protein Binding
  • Models, Molecular
  • Kinetics
  • GTPase-Activating Proteins
  • GTP-Binding Proteins
  • GTP Phosphohydrolases
  • Fluorescence