PMID: 2502397Jul 15, 1989Paper

Evidence for receptor-regulated phosphotransfer reactions involved in activation of the adenylate cyclase inhibitory G protein in human platelet membranes

European Journal of Biochemistry
K H Jakobs, T Wieland

Abstract

The activity of the adenylate cyclase inhibitory guanine-nucleotide-binding regulatory protein (Gi), measured as inhibition of forskolin-stimulated cyclic AMP formation, and its regulation by various nucleotides and the inhibitory alpha 2-adrenoreceptor agonist epinephrine was studied in membranes of human platelets. When adenylate cyclase activity was measured with ATP as substrate and in the absence of a nucleoside-triphosphate-regenerating system, GTP (0.1-10 microM) by itself potently and efficiently inhibited the enzyme. GDP was almost as potent and as effective as GTP. In the additional presence of epinephrine, the potencies of both GTP and GDP were increased about threefold, while maximal inhibition by these nucleotides was only slightly increased by the receptor agonist. In contrast to GTP and GDP, the metabolically stable GDP analog, guanosine 5'-[beta-thio]diphosphate, had only a very small effect, suggesting that GDP but not its stable analog is converted to the active GTP. Addition of UDP (1 mM), used to block the GDP to GTP conversion reaction, completely suppressed the inhibitory effect of GDP, while that caused by GTP was not affected. Most important, the inhibitory receptor agonist epinephrine counteracted the s...Continue Reading

References

Jan 1, 1986·Annual Review of Cell Biology·L Stryer, H R Bourne
Aug 1, 1987·Kidney International·M M SchwartzE J Lewis
Apr 1, 1980·Thrombosis Research·K P Mellwig, K H Jakobs
Jul 27, 1983·Biochimica Et Biophysica Acta·K H Jakobs, K Aktories

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Citations

Feb 1, 1992·Trends in Pharmacological Sciences·M L Lacombe, K H Jakobs
May 16, 2008·The Journal of Biological Chemistry·Magnus GrenegårdTomas L Lindahl
May 19, 2019·Naunyn-Schmiedeberg's Archives of Pharmacology·Klaus AktoriesThomas Wieland
Jan 26, 2012·Platelets·Erik TournoijJan-Willem N Akkerman

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