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Inhibition of hormonally regulated adenylate cyclase by the beta gamma subunit of transducin.
Author(s) -
Bockaert J.,
Deterre P.,
Pfister C.,
Guillon G.,
Chabre M.
Publication year - 1985
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1985.tb03795.x
Subject(s) - transducin , cyclase , biology , adenylate kinase , phosphodiesterase , g protein , beta (programming language) , protein subunit , gtp' , gtp binding protein regulators , gamma subunit , g alpha subunit , biochemistry , microbiology and biotechnology , receptor , enzyme , gene , computer science , programming language
Transducin (T), the GTP‐binding protein of the retina activates the cGMP phosphodiesterase system, and presents analogies with the proteins GS and Gi which respectively mediate adenylate cyclase activation and inhibition by hormone receptors. These proteins are all comprised of an alpha subunit carrying the GTP‐binding site and a beta gamma subunit made of two peptides. The beta peptide (35 kd) appears similar in the three proteins. We demonstrate here that purified T beta gamma inhibits adenylate cyclase from human platelet membranes. This inhibition was observed when adenylate cyclase was stimulated by GTP, prostaglandin E1 (PGE1), NaF and forskolin, but not when stimulated by GTP(gamma)S. In the presence of GTP and forskolin, the T beta gamma‐induced maximal inhibition was not additive with the alpha 2‐receptor‐induced adenylate cyclase inhibition mediated by Gi. Both inhibitions were suppressed at high Mg2+ concentrations, which as also known to dissociate T beta gamma from T alpha‐GDP. This suggests that these adenylate cyclase inhibitions are due to the formation of inactive complexes of GS alpha‐GDP with T beta gamma or Gi beta gamma. T beta gamma‐induced inhibition did not require detergent and could be suppressed by simple washing. T beta gamma effects are dependent on its concentration rather than on its total amount. This suggests that T beta gamma can operate in solution with no integration into the membrane. Similar inhibitory effects of T beta gamma are observed on adenylate cyclase from anterior pituitary and lymphoma S49 cell lines.