Small GTP-Binding Proteins and Intracellular Messenger Systems

有一个类似Ras p21/ras p21的超家族--与GTPase活性的小GTP-binding蛋白（小G蛋白）。有超过40名成员被报告，其中20，000和41，000名妇女都是由一个单一的、负责任的多肽组成的。证据是累积的，当小G蛋白进入内部信使系统时。在这个研究项目中，我们调查了帖子-翻译修改、激活模式和小G蛋白的功能。大多数小G蛋白都有独特的共识C-终端动机至少含有一个半胱氨酸居住者。我们已经找到了smg p21 B、rhoA p21和smg p25 A的C-终端半胱氨酸保留地，并且这些prenylation都是每个小G蛋白绑定到膜的必要条件。小G蛋白有两种可转换形式，一种是GDP绑定的非活性形式，另一种是GDP绑定的非活性形式。从GDP-绑定到GDP-绑定表格的转换和GD的反向转换被定义为 ... More P/GTP交换和GTPase反应，尊重。我们有几种GDP/GTP交换蛋白（GDP分离刺激剂（GDS）和GDP分离抑制剂（GDI） ）和GTPase激活蛋白（GAP）。GDS和GDI还对小G蛋白与薄膜的结合进行了管制。GTP-结合形式的小G蛋白与其特定效应蛋白质的相互作用，并退出其特定行为。Smgp 21 B与ras p21 GAP的相互作用，并抑制ras p21 GAP活动。由于smg p21 B被蛋白激酶A磷酸化，这是可以想象的，因为smg p21 B存在于蛋白激酶A的下游。我们还发现了smgp 25 A在规范的秘密细胞中检测到，但不在稳定的秘密细胞中。Since in most of regulated secretory cells secretion is stimulated by the activation of protein kinase C and the Ca^<2+> mobilization，smgp25A might be present in the down stream of protein kinase C and Ca^<2+>。这些结果建议小G蛋白及其调节性蛋白被已知良好的内部信使系统调节，并为内部调节性机制构建一个庞大的网络。Less（低）

There is a superfamily of ras p21/ras p21-like small GTP-binding proteins (small G proteins) with GTPase activity. Over forty members have been reported, and all of them with Mrs between 20,000 and 41,000 are composed of a single respective polypeptide. Evidence is accumulating that small G proteins are involved in intracellular messenger systems. In this research project, We have investigated the postーtranslational modifications, the modes of activation and the functions of small G proteins. Most of small G proteins have the unique consensus C-terminal motifs containing at least one cysteine residue. We have found that the C-terminal cysteine residues of smg p21B, rhoA p21 and smg p25A are geranygeranylated and that these prenylations are essential for each small G protein to bind to membranes. Small G proteins have two interconvertible forms, GDP-bound inactive and GTP-bound active forms. The conversion from the GDP-bound to GTP-bound form and the reverse conversion are induced by GD … More P/GTP exchange and GTPase reactions, respectively. We have purified and characterized several GDP/GTP exchange proteins (GDP dissociation stimulator (GDS) and GDP Dissociation inhibitor (GDI) ) and GTPase activating Proteins (GAP) for small G Proteins. GDS and GDI also regulate the binding of small G proteins to membranes. The GTP-bound form small G proteins interact with their specific effector proteins proteins and exert their specific actions. Smg p21B interacts with ras p21 GAP and inhibits the ras p21 GAP activity for ras p21. Since smg p21B is phosphorylated by protein kinase A, it is conceivable that smg p 21B is present in the down stream of protein kinase A. We have also found that smg p25A is detected in regulated secretory cells but not in constitutive secretory cells. Since in most of regulated secretory cells secretion is stimulated by the activation of protein kinase C and the Ca^<2+> mobilization, smg p25A might be present in the down stream of protein kinase C and Ca^<2+>. These results suggest that small G proteins and their regulatory proteins are regulat ed by well-known intracellular messenger systems and constitute a huge network with them for intracellular regulatory mechanisms. Less