Lad P M, Nielsen T B, Preston M S, Rodbell M
J Biol Chem. 1980 Feb 10;255(3):988-95.
Several changes were noted in the characteristics of the turkey erythrocyte beta-adrenergic receptor and in the kinetic properties of adenylate cyclase following pretreatment of erythrocyte membranes with isoproterenol and GMP, and thorough washing to remove these agents. The changes include modifications in the binding of agonist (isoproterenol) and in revelation of marked effects of GTP on agonist binding; reduction in the lag in Gpp(NH)p activation of adenylate cyclase; short lived activation by GTP which is lengthened by treatment with cholera toxin and NAD prior to pretreatment with isoproterenol and GMP. Treatment with cholera toxin also shortened the lag in activation by Gpp(NH)p and increased the steady state levels of activation by both Gpp(NH)p and GTP. The following conclusions can be drawn: (i) catecholamines, in the presence of a guanine nucleotide, stimulate the exchange of bound and exogenous nucleotide; (ii) the exchange reaction is involved in both the activation of adenylate cyclase and in the reciprocal effects of hormone and guanine nucleotides on each other's binding: (iii) the beta-adrenergic receptor and nucleotide regulatory components are linked in turkey erythrocyte membranes; (iv) both cholera toxin and catecholamines, although by different mechanisms, stimulate the exchange reaction at the nucleotide regulatory sites.
在用异丙肾上腺素和鸟苷酸预处理红细胞膜并彻底洗涤以去除这些试剂后，观察到火鸡红细胞β-肾上腺素能受体的特性以及腺苷酸环化酶的动力学性质发生了若干变化。这些变化包括激动剂（异丙肾上腺素）结合的改变以及GTP对激动剂结合的显著影响的显现；腺苷酸环化酶被Gpp(NH)p激活时延迟的减少；GTP引起的短暂激活，在用异丙肾上腺素和鸟苷酸预处理之前先用霍乱毒素和NAD处理可延长这种激活；用霍乱毒素处理还缩短了被Gpp(NH)p激活时的延迟，并增加了被Gpp(NH)p和GTP激活的稳态水平。可以得出以下结论：(i) 在鸟嘌呤核苷酸存在的情况下，儿茶酚胺刺激结合的核苷酸与外源核苷酸的交换；(ii) 交换反应既参与腺苷酸环化酶的激活，也参与激素和鸟嘌呤核苷酸对彼此结合的相互影响；(iii) 在火鸡红细胞膜中，β-肾上腺素能受体和核苷酸调节成分是相连的；(iv) 霍乱毒素和儿茶酚胺虽然机制不同，但都刺激核苷酸调节位点的交换反应。
