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Sites of interaction between rod G-protein alpha-subunit and cGMP-phosphodiesterase gamma-subunit. Implications for the phosphodiesterase activation mechanism.

Publication ,  Journal Article
Artemyev, NO; Rarick, HM; Mills, JS; Skiba, NP; Hamm, HE
Published in: J Biol Chem
December 15, 1992

In photoreceptor cells of vertebrates light activates a series of protein-protein interactions resulting in activation of a cGMP-phosphodiesterase (PDE). Interaction between the GTP-bound form of rod G-protein alpha-subunit (alpha t) and PDE inhibitory gamma-subunit (P gamma) is a key event for effector enzyme activation. This interaction has been studied using P gamma labeled with the fluorescent probe, lucifer yellow vinyl sulfone, at Cys-68 (P gamma LY) and sites of interaction on alpha t and P gamma have been investigated. Addition of alpha tGTP gamma S to P gamma LY produced a 3.2-fold increase in the fluorescence of P gamma LY. The Kd for alpha tGTP gamma S.P gamma LY interaction was 36 nM. Addition of 1 microM alpha tGDP had no effect, but in the presence of A1F4-, alpha tGDP increased P gamma LY fluorescence by 85%. When P gamma LY was reconstituted with P alpha beta to form fluorescent holo-PDE, alpha tGTP gamma S increased the fluorescence of holo-PDE with a K0.5 = 0.7 microM. Also, alpha tGTP gamma S stimulated the activity of this PDE over an identical range of concentrations with a similar K0.5 (0.6 microM). alpha tGTP gamma S enhanced the fluorescence of a COOH-terminal P gamma fragment, P gamma LY-46-87, as well (Kd = 1.5 microM). We demonstrate that an alpha t peptide, alpha t-293-314, which activated PDE (Rarick, H. M., Artemyev, N. O., and Hamm, H. E. (1992) Science 256, 1031-1033), mediates PDE activation by interacting with the P gamma-46-87 region. Peptide alpha t-293-314 bound to P gamma LY (K0.5 = 1.2 microM) as well as to the carboxyl-terminal P gamma fragment, P gamma LY-46-87 (K0.5 = 1.7 microM) as measured by fluorescence increase, while other alpha t peptides had no effect. A peptide from the P gamma central region, P gamma-24-46, blocked the interaction between alpha tGTP gamma S and P gamma LY. The Kd for alpha tGTP gamma S.P gamma-24-46 interaction was 0.7 microM. On the other hand, P gamma-24-46 had no effect on alpha t-293-314 interaction with P gamma LY. Our data suggest that there are at least two distinct sites of interaction between alpha tGTP gamma S and P gamma. The interaction between alpha t-293-314 and P gamma-46-87 is important for PDE activation.(ABSTRACT TRUNCATED AT 400 WORDS)

Duke Scholars

Published In

J Biol Chem

ISSN

0021-9258

Publication Date

December 15, 1992

Volume

267

Issue

35

Start / End Page

25067 / 25072

Location

United States

Related Subject Headings

  • Photoreceptor Cells
  • Peptides
  • Molecular Sequence Data
  • Macromolecular Substances
  • Kinetics
  • Guanine Nucleotides
  • GTP-Binding Proteins
  • Enzyme Activation
  • Cell Membrane
  • Cattle
 

Citation

APA
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ICMJE
MLA
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Artemyev, N. O., Rarick, H. M., Mills, J. S., Skiba, N. P., & Hamm, H. E. (1992). Sites of interaction between rod G-protein alpha-subunit and cGMP-phosphodiesterase gamma-subunit. Implications for the phosphodiesterase activation mechanism. J Biol Chem, 267(35), 25067–25072.
Artemyev, N. O., H. M. Rarick, J. S. Mills, N. P. Skiba, and H. E. Hamm. “Sites of interaction between rod G-protein alpha-subunit and cGMP-phosphodiesterase gamma-subunit. Implications for the phosphodiesterase activation mechanism.J Biol Chem 267, no. 35 (December 15, 1992): 25067–72.

Published In

J Biol Chem

ISSN

0021-9258

Publication Date

December 15, 1992

Volume

267

Issue

35

Start / End Page

25067 / 25072

Location

United States

Related Subject Headings

  • Photoreceptor Cells
  • Peptides
  • Molecular Sequence Data
  • Macromolecular Substances
  • Kinetics
  • Guanine Nucleotides
  • GTP-Binding Proteins
  • Enzyme Activation
  • Cell Membrane
  • Cattle