Freissmuth M, Casey P J, Gilman A G
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235.
FASEB J. 1989 Aug;3(10):2125-31.
Hormones, neurotransmitters, and autacoids interact with specific receptors and thereby trigger a series of molecular events that ultimately produce their biological effects. These receptors, localized in the plasma membrane, carry binding sites for ligands as diverse as peptides (e.g., glucagon, neuropeptides), lipids (e.g., prostaglandins), nucleosides and nucleotides (e.g., adenosine), and amines (e.g., catecholamines, serotonin). These receptors do not interest directly with their respective downstream effector (i.e., an ion channel and/or an enzyme that synthesizes a second messenger); rather, they control one or several target systems via the activation of an intermediary guanine nucleotide-binding regulatory protein or G protein. G proteins serve as signal transducers, linking extracellularly oriented receptors to membrane-bound effectors. Traffic in these pathways is regulated by a GTP (on)-GDP (off) switch, which is regulated by the receptor. The combination of classical biochemistry and recombinant DNA technology has resulted in the discovery of many members of the G protein family. These approaches, complemented in particular by electrophysiological experiments, have also identified several effectors that are regulated by G proteins. We can safely assume that current lists of G proteins and the functions that they control are incomplete.
激素、神经递质和自分泌调节因子与特定受体相互作用，从而引发一系列分子事件，最终产生它们的生物学效应。这些位于质膜上的受体带有多种配体的结合位点，这些配体包括肽（如胰高血糖素、神经肽）、脂质（如前列腺素）、核苷和核苷酸（如腺苷）以及胺类（如儿茶酚胺、5-羟色胺）。这些受体并不直接与它们各自的下游效应器（即离子通道和/或合成第二信使的酶）相互作用；相反，它们通过激活一种中间的鸟嘌呤核苷酸结合调节蛋白或G蛋白来控制一个或几个靶系统。G蛋白作为信号转导器，将细胞外的受体与膜结合效应器连接起来。这些信号通路中的信号传递由一个GTP（开启）-GDP（关闭）开关调节，该开关受受体调控。经典生物化学和重组DNA技术的结合导致了许多G蛋白家族成员的发现。这些方法，特别是通过电生理实验得到补充，也确定了几种受G蛋白调节的效应器。我们可以有把握地假设，目前G蛋白及其所控制功能的列表并不完整。
