G alpha (i):RGS dissociates to inactive G alpha (i)–i1/i2/i3

G Protein Coupled Receptors (GPCR) sense extracellular signals and activate different Guanine nucleotide binding proteins (G proteins). Upon activation, GPCRs can replace the GDP with GTP in the alpha subunit of G proteins. GTP binding modifies the conformation of G alpha proteins and activates them. The Regulator of G protein Signalling (RGS) are GTPase Accelerating Proteins (GAPs) that can directly inhibit the G alpha subunit activity. There are at least 25 different types of RGS proteins known. Several of these RGS proteins (1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21) can bind and stabilize the transition state of Guanine nucleotide binding protein G(i) subunit alpha (GNAI). Subsequently, RGS proteins in the complex facilitate the hydrolyses of GNAI:GTP to GNAI:GDP. Following this, the complex dissociates releasing inactive GNAI (Neubig & Siderovski 2002, Kach et al. 2012).

G蛋白偶联受体（G Protein Coupled Receptors, GPCR）能够感知细胞外信号并激活多种鸟苷酸结合蛋白（G蛋白）。在激活状态下，GPCR能够将G蛋白的α亚基中的GDP替换为GTP。GTP的结合改变了Gα蛋白的构象，从而激活其功能。G蛋白信号通路的调节因子（Regulator of G protein Signalling, RGS）是一类GTP酶加速蛋白（GTPase Accelerating Proteins, GAPs），能够直接抑制G蛋白α亚基的活性。目前已知的RGS蛋白至少有25种。其中一些RGS蛋白（1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21）能够结合并稳定鸟苷酸结合蛋白G(i)亚基α（GNAI）的过渡态。随后，RGS蛋白在复合物中促进GNAI:GTP向GNAI:GDP的水解。此后，复合物解离，释放出非活性状态的GNAI（Neubig & Siderovski 2002, Kach et al. 2012）。