Schramm M, Selinger Z
Science. 1984 Sep 21;225(4668):1350-6. doi: 10.1126/science.6147897.
The adenylate cyclase system is composed of an activating hormone or neurotransmitter (H), its receptor (R), the guanosine triphosphate (GTP) binding protein (Gs), and the catalytic unit (C). The activation of the receptor R involves a transient change in conformation, from a loose binding of the neurotransmitter H to an extremely tight interaction, termed locking. The system is regulated in the activation steps and also by three deactivation processes. A guanosine triphosphatase activity is built into the Gs protein so that the active GsGTP has only a limited lifetime during which it is able to activate C. In addition, the continued occupation of R by H causes desensitization of R. Finally, there are inhibitory receptors, such as alpha-adrenergic and opiate receptors, which inhibit the adenylate cyclase by way of a specific GTP binding protein (Gi). Yet to be determined are the conformational transformations of pure R on binding of an agonist or a partial agonist; the genes that code for the many different receptors that activate the adenylate cyclase, and the possibility that the G components interact with systems in the cell other than the adenylate cyclase.
腺苷酸环化酶系统由一种激活激素或神经递质（H）、其受体（R）、鸟苷三磷酸（GTP）结合蛋白（Gs）和催化单位（C）组成。受体R的激活涉及构象的瞬时变化，从神经递质H的松散结合到一种极其紧密的相互作用，称为锁定。该系统在激活步骤以及三个失活过程中受到调节。Gs蛋白具有鸟苷三磷酸酶活性，因此活性GsGTP的寿命有限，在此期间它能够激活C。此外，H持续占据R会导致R脱敏。最后，存在抑制性受体，如α-肾上腺素能受体和阿片受体，它们通过一种特定的GTP结合蛋白（Gi）抑制腺苷酸环化酶。尚待确定的是，纯R在结合激动剂或部分激动剂时的构象转变；编码激活腺苷酸环化酶的许多不同受体的基因，以及G成分与细胞中除腺苷酸环化酶之外的其他系统相互作用的可能性。
