许多化学、物理信号若不经过细菌膜受体而启动一系列反应便不能直接进入细胞内，其中有相当部分的细胞外信号要通过Ｇ蛋白转导为细胞内效应。目前已知能与Ｇ蛋白偶联的受体有数百种，这类受体的共同特点是具有七个跨膜区，是很大一类受体蛋白，虽然它们都跨膜七次，但各自氨基 Many chemical and physical signals can not directly enter the cell if they initiate a series of reactions without passing through bacterial membrane receptors, and a considerable portion of extracellular signals are transduced by G proteins into intracellular effects. It is known that there are hundreds of receptors that can be coupled with G protein. The common feature of these receptors is that they have seven transmembrane domains and are a large class of receptor proteins. Although they all transmembrane seven times, Amino