Membrane targeting of G protein

G 蛋白的膜靶向

• 批准号: 6432126
• 负责人: TERESA L Z JONES
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6432126
• 关键词: G protein; fatty acylation; high performance liquid chromatography; membrane activity; membrane proteins; membrane structure; myristates; nitric oxide; palmitates; posttranslational modifications; protein structure; protein structure function; receptor coupling; receptor expression

Heterotrimeric G proteins sit at the cytoplasmic face of membranes and transduce signals. Palmitoylation occurs on most of the alpha subunits in the family of heterotrimeric G proteins. During an activation cycle, G alpha subunits communicate with G beta/gamma subunits, receptors, effectors and RGS proteins with palmitoylation modulating many of these protein interactions. In addition, palmitoylation can localize proteins to and within specific membrane sites. The localization of a splice variant of G alpha s, XL alpha s, to the Golgi complex is due, in part, to palmitoylation of cysteine residues adjacent to a Golgi targeting signal. Within membranes, palmitoylation can target proteins to microdomains, characterized by their resistance to detergents and enrichment in sphingolipids and cholesterol. G proteins are found in these microdomains, named rafts. Depletion of cellular cholesterol or sphingolipids disrupted the raft localization of G alpha s, but receptor-activated signaling through Gs remained intact suggesting that raft localization is not required for this function of Gs. Palmitoylation is a reversible modification with an increase in palmitate turnover on the G alpha subunit upon activation by a receptor. The enzymes responsible for reversible thioacylation have been elusive. A strong candidate for the thioesterase that removes palmitate is the 25-kDa protein, acyl-protein thioesterase 1 (APT1). Both APT1 and an isoform, APT2, (67% identical) are soluble proteins and expressed ubiquitously. The crystal structure of the human form of APT1 was solved to 1.8 angstrom resolution and showed that APT1 is a member of the alpha/beta hydrolase family, which includes other acylhydrolases such as the palmitoyl protein thioesterase. APT1 appears to be dimeric with the substrate-binding pocket and active site occluded by the dimer interface suggesting that dissociation occurs upon interaction with the substrate.

异三聚体G蛋白位于膜的细胞质面部和传感信号。 棕榈酰化发生在异三聚体G蛋白家族中的大多数α亚基上。在激活周期中，Gα亚基与Gβ/伽马亚基，受体，效应子和RGS蛋白具有棕榈酰化调节许多这些蛋白质相互作用。 另外，棕榈酰化可以将蛋白质定位于特定的膜位点。 Galpha s，Xl alpha s的剪接变体与高尔基体配合物的定位部分是由于与高尔基靶信号相邻的半胱氨酸残基的棕榈酰化。 在膜内，棕榈酰化可以靶向蛋白质，其特征在于它们对洗涤剂的耐药性和在鞘脂和胆固醇中的富集为特征。 G蛋白在这些微区域中发现，称为筏。 细胞胆固醇或鞘脂的耗竭破坏了G alpha s的筏定位，但是通过GS进行受体激活的信号传导仍然完好无损，这表明GS的这种功能不需要筏定位。棕榈酰化是一种可逆的修饰，在受体激活后，Gα亚基上棕榈酸酯的周转率增加。 负责可逆硫囊肿的酶是难以捉摸的。 去除棕榈酸酯的硫酯酶的强大候选者是25 kDa蛋白，酰基蛋白硫酯酶1（APT1）。 APT1和同工型，APT2（67％相同）都是可溶蛋白，并且无处不在。 APT1的人类形式的晶体结构已溶液到1.8 Angstrom分辨率，并表明APT1是α/β水解酶家族的成员，其中包括其他酰基氢酶，例如棕榈酰蛋白硫酯酶。 APT1似乎与底物结合口袋和由二聚体界面遮住的活性位点二聚体，这表明与底物相互作用时发生解离。