Lambert Nevin A
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912-2300, USA.
Sci Signal. 2008 Jun 24;1(25):re5. doi: 10.1126/scisignal.125re5.
Heterotrimeric G proteins dissociate into their component Galpha and Gbetagamma subunits when these proteins are activated in solution. Until recently, it has not been known if subunit dissociation also occurs in cells. The development of optical methods to study G protein activation in live cells has made it possible to demonstrate heterotrimer dissociation at the plasma membrane. However, subunit dissociation is far from complete, and many active [guanosine triphosphate (GTP)-bound] heterotrimers are intact in a steady state. This unexpectedly reluctant dissociation calls for inclusion of a GTP-bound heterotrimeric state in models of the G protein cycle and places renewed emphasis on the relation between subunit dissociation and effector activation.
当异源三聚体G蛋白在溶液中被激活时，它们会解离成其组成成分α亚基和βγ亚基。直到最近，人们还不清楚亚基解离是否也发生在细胞中。用于研究活细胞中G蛋白激活的光学方法的发展使得在质膜上证明异源三聚体解离成为可能。然而，亚基解离远未完成，许多处于稳态的活性（结合鸟苷三磷酸（GTP）的）异源三聚体是完整的。这种出乎意料的解离迟缓要求在G蛋白循环模型中纳入结合GTP的异源三聚体状态，并重新强调亚基解离与效应器激活之间的关系。
