G Protein Beta-Gamma and Beta-RGS Dimers--Structure and

g蛋白或鸟嘌呤核苷酸结合调节蛋白是异源三聚体，通过将细胞外刺激受体偶联到细胞内效应器（酶、离子通道），作为跨膜信号转导器发挥作用。g蛋白构成了一个多样化的家族，以特定的受体和效应相互作用为特征，而受体和效应相互作用又由三个组成亚基的结构决定。α亚基结合鸟嘌呤核苷酸，并在效应调节中具有良好的作用。β亚基和γ亚基紧密结合为β - γ复合物，组成一个单一的功能实体，与α亚基一样，是G蛋白与受体相互作用所必需的。β - γ复合物的效应调节作用现在被许多细胞系统所接受。目前的研究强调β - γ复合物在g蛋白介导的信号转导中的作用。Mel Simon和他的同事从大脑中克隆出了一种结构上分化的神经表达的G β亚基-5，后来在视网膜中发现了一种选择性拼接的“长”形式（G β 5- l）。最近发现G β -5表现出功能专门化，因为它能够激活PLC，但不能激活MAPK或JNK级联。我们实验室目前的工作是利用黑腹果蝇和培养的PC12细胞作为模型系统，研究昆虫G β -5同源物和哺乳动物G β -5的共同功能。

G-proteins, or guanine-nucleotide binding regulatory proteins, are heterotrimers which function as transmembrane signal transducers by coupling receptors for extracellular stimuli to intracellular effectors (enzymes, ion channels). G-proteins constitute a diverse family distinguished by specific receptor and effector interactions which in turn are determined by the structure of the three constituent subunits. The alpha subunit binds guanine nucleotides and has a well-established role in effector modulation. The beta and gamma subunits are tightly associated as a beta-gamma complex, comprising a single functional entity which, like the alpha subunit, is absolutely required for G protein interaction with receptor. An effector-regulatory role for the beta-gamma complex is now accepted in many cellular systems. The present research emphasizes the role of the beta-gamma complex in G-protein-mediated signal transduction. A structurally divergent neurally expressed G beta subunit, beta-5, was cloned from brain by Mel Simon and coworkers, and later found in an alternatively spliced "long" form in retina (G beta5-L). G beta-5 was recently found to exhibit functional specialization, as it was able to activate PLC but not the MAPK or JNK cascades. Current work in our laboratory examines shared functions of the insect G beta-5 homolog and mammalian G beta-5, using Drosophila melanogaster and cultured PC12 cells as model systems.