Guanine nucleotide binding regulatory protein

Based on these findings and a large number of parallel observations of /3-adre-nergic receptor-mediated activation of adenylate cyclase in other cells [33,37], a model has been developed to explain the interactions between receptors that are 

Interaction of the receptor with Gs also alters the receptor to a state with high affinity for agonist [37,47-49], whereas addition of nonhydrolyzable GTP analogues disrupts the association and converts the receptor to low affinity state [47-49]. Thus the increased binding of GTP to Gs induced by occupancy of the receptor by hormone [45] leads secondarily to dissociation of the receptor from Gs and a return of the receptors to a low affinity state [37,49]. Due to the GTPase activity of Gs, as GTP is also converted to c GDP which reassociates with the jBy complex to form inactive GS-GDP. As a result of the conversion of as-GTP to as GDP, activation of adenylate cyclase ceases unless hormone continues to be present to initiate another cycle of activation. 

It is obvious from the above description that many mechanistic and molecular details of the hormonal activation of adenylate cyclase are still unknown, but it seems unlikely that the scheme presented will require major modification. 

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FIGURE 25.1 Amrinone exerts positive inotropic and vasodilating actions. AMP = adenosine monophosphate, AC = adenlate cyclase, PDE = phosphodiesterase, Gs = stimulatory guanine nucleotide-binding regulatory protein. 

G proteins guanine nucleotide binding regulatory proteins Gl first gap in mitotic cell cycle G2 second gap in mitotic cell cycle... 

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The Guanine Nucleotide-Binding Regulatory Protein in Cell Membranes as the Specific Substrate of lAP-Catalyzed ADP-Ribosylation... 

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In the cAMP system, occupancy of an appropriate receptor in the plasma membrane by its complementary hormone triggers the activation of adenylate cyclase via guanine nucleotide-binding regulatory proteins (G proteins). Positive stimuli... 

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