Abstract
Guanine nucleotide binding proteins (G proteins) couple receptors to a variety of effector systems. These proteins are heterotrimers, consisting of α, β and γ subunits. Activation of G proteins by agonist-occupied receptors results in GTP-GDP exchange at the α-subunits, followed by dissociation of the βγ subunits. In the case of Gs, the αs-GTP species can then activate adenylate cyclase directly. Inhibition of adenylate cyclase, on the other hand, results from the binding of βγ released from the dissociation of Gi with free αs-GTP, thereby preventing activation of adenylate cyclase. Termination of G protein activation is mediated by GTPase activity intrinsic to the a subunits, which cleaves α-GTP to inactive α-GDP. The resulting α-GDP complexes can then reassociate with the βγ subunits to reform the heterotrimeric proteins (Gilman, 1987).
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Ramkumar, V., Stiles, G.L. (1990). Inhibition of the Function of Guanine Nucleotide Binding Proteins by the New Positive Inotropes. In: Jacobson, K.A., Daly, J.W., Manganiello, V. (eds) Purines in Cellular Signaling. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-3400-5_34
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DOI: https://doi.org/10.1007/978-1-4612-3400-5_34
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