Imaizumi T, Watanabe Y, Yoshida H
Department of Pharmacology I, Osaka University, School of Medicine, Japan.
Eur J Pharmacol. 1991 Jul 12;207(3):189-94. doi: 10.1016/0922-4106(91)90030-l.
Pretreatment of partially purified inhibitory GTP-binding protein (Gi, 41 kDa) with activated cyclic AMP-dependent protein kinase (PKA) decreases its ADP-ribosylation by islet-activating protein (pertussis toxin, IAP). We examined whether this decrease was associated with dissociation of the trimer of alpha beta gamma-subunits of Gi protein into alpha-subunits and beta gamma-subunits. Results showed that phosphorylation of the Gi protein by PKA impaired its dissociation into alpha-subunits and beta gamma-subunits by 50 mM Mg2+ and 100 microM GTP gamma S. The results suggested that phosphorylation of the Gi protein by PKA possibly caused a conformational change of the trimer Gi protein.
用活化的环磷酸腺苷依赖性蛋白激酶（PKA）对部分纯化的抑制性GTP结合蛋白（Gi，41 kDa）进行预处理，可降低其被胰岛激活蛋白（百日咳毒素，IAP）ADP核糖基化的程度。我们研究了这种降低是否与Gi蛋白的αβγ亚基三聚体解离为α亚基和βγ亚基有关。结果表明，PKA对Gi蛋白的磷酸化作用使其在50 mM Mg2+和100 μM GTPγS作用下解离为α亚基和βγ亚基的能力受损。结果提示，PKA对Gi蛋白的磷酸化可能导致三聚体Gi蛋白发生构象变化。
