Effects of phosphorylation of inhibitory GTP-binding protein by cyclic AMP-dependent protein kinase on its ADP-ribosylation by pertussis toxin, islet-activating protein |
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Authors: | Y Watanabe T Imaizumi N Misaki K Iwakura H Yoshida |
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Affiliation: | Department of Pharmacology I, Osaka University, School of Medicine, Japan. |
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Abstract: | Pretreatment of rat cardiac myocytes with the beta-adrenergic agonist, db-cAMP or forskolin decreased ADP-ribosylation of 40-41 kDa protein by islet-activating protein (IAP) in cell membranes. Addition of activated cyclic AMP-dependent protein kinase (protein kinase A) catalytic subunit and MgCl2 also decreased ADP-ribosylation of 40-41 kDa protein by IAP in cell membranes. The alpha- and beta-subunits of partially purified inhibitory GTP-binding protein (Gi) were both phosphorylated by protein kinase A. The amounts of phosphate incorporated into the subunits of Gi were 0.34 and 0.18 mol/mol protein. These show that phosphorylation of Gi by protein kinase A results in a decrease in its ADP-ribosylation by IAP. |
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