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The effector enzyme regulates the duration of G protein signaling in vertebrate photoreceptors by increasing the affinity between transducin and RGS protein.

Publication ,  Journal Article
Skiba, NP; Hopp, JA; Arshavsky, VY
Published in: J Biol Chem
October 20, 2000

The photoreceptor-specific G protein transducin acts as a molecular switch, stimulating the activity of its downstream effector in its GTP-bound form and inactivating the effector upon GTP hydrolysis. This activity makes the rate of transducin GTPase an essential factor in determining the duration of photoresponse in vertebrate rods and cones. In photoreceptors, the slow intrinsic rate of transducin GTPase is accelerated by the complex of the ninth member of the regulators of G protein signaling family with the long splice variant of type 5 G protein beta subunit (RGS9.Gbeta5L). However, physiologically rapid GTPase is observed only when transducin forms a complex with its effector, the gamma subunit of cGMP phosphodiesterase (PDEgamma). In this study, we addressed the mechanism by which PDEgamma regulates the rate of transducin GTPase. We found that RGS9.Gbeta5L alone has a significant ability to activate transducin GTPase, but its affinity for transducin is low. PDEgamma acts by enhancing the affinity between activated transducin and RGS9.Gbeta5L by more than 15-fold, which is evident both from kinetic measurements of transducin GTPase rate and from protein binding assays with immobilized transducin. Furthermore, our data indicate that a single RGS9.Gbeta5L molecule is capable of accelerating the GTPase activity of approximately 100 transducin molecules/s. This rate is faster than the rates reported previously for any RGS protein and is sufficient for timely photoreceptor recovery in both rod and cone photoreceptors.

Duke Scholars

Published In

J Biol Chem

DOI

ISSN

0021-9258

Publication Date

October 20, 2000

Volume

275

Issue

42

Start / End Page

32716 / 32720

Location

United States

Related Subject Headings

  • Transducin
  • Signal Transduction
  • Rod Cell Outer Segment
  • RGS Proteins
  • Photoreceptor Cells, Vertebrate
  • Kinetics
  • Heterotrimeric GTP-Binding Proteins
  • GTP Phosphohydrolases
  • Cell Membrane
  • Cattle
 

Citation

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Skiba, N. P., Hopp, J. A., & Arshavsky, V. Y. (2000). The effector enzyme regulates the duration of G protein signaling in vertebrate photoreceptors by increasing the affinity between transducin and RGS protein. J Biol Chem, 275(42), 32716–32720. https://doi.org/10.1074/jbc.C000413200
Skiba, N. P., J. A. Hopp, and V. Y. Arshavsky. “The effector enzyme regulates the duration of G protein signaling in vertebrate photoreceptors by increasing the affinity between transducin and RGS protein.J Biol Chem 275, no. 42 (October 20, 2000): 32716–20. https://doi.org/10.1074/jbc.C000413200.
Skiba, N. P., et al. “The effector enzyme regulates the duration of G protein signaling in vertebrate photoreceptors by increasing the affinity between transducin and RGS protein.J Biol Chem, vol. 275, no. 42, Oct. 2000, pp. 32716–20. Pubmed, doi:10.1074/jbc.C000413200.

Published In

J Biol Chem

DOI

ISSN

0021-9258

Publication Date

October 20, 2000

Volume

275

Issue

42

Start / End Page

32716 / 32720

Location

United States

Related Subject Headings

  • Transducin
  • Signal Transduction
  • Rod Cell Outer Segment
  • RGS Proteins
  • Photoreceptor Cells, Vertebrate
  • Kinetics
  • Heterotrimeric GTP-Binding Proteins
  • GTP Phosphohydrolases
  • Cell Membrane
  • Cattle