CHARACTERIZATION OF A NOVEL G PROTEIN IN HUMAN PLATELETS

该提案将研究40 kDa蛋白质的结构和功能 我们认为血小板是鸟嘌呤的α亚单位 核苷酸结合调节蛋白或G蛋白。根据我们最近的 研究表明，这种蛋白质具有几种新的特性。一是 在血小板活化过程中磷酸化，显然是通过蛋白激酶C。 其次，它与G（z-alpha）具有免疫交叉反应性， 从两个非血小板cDNA文库中克隆的α亚基， 但还没有被隔离。第三，与其他G蛋白相比， 它一直是血小板研究的焦点，它既不是ADP-核糖基化的，也不是ADP-核糖基化的。 百日咳毒素也不被已知的百日咳毒素特异性的抗血清识别， 百日咳毒素敏感的G蛋白，如G（i-α）。即使G（z- α）是蛋白激酶C的底物，我们有 在1999年， 确认两种蛋白质的免疫交叉反应性。 我们研究的目标是了解 G（z-alpha）（plt）。具体地说，我们将：（1）确定G（z-1）的恒等式。 α）（plt），并定义其与G（z-alpha）的关系，（2）确定 G（z-alpha）（plt）被磷酸化的位点，（3）确定 磷酸化的生化后果和（4）定义G（z-）的作用， α）（PLT）的血小板功能。

This proposal will examine the structure and function of a 40 kDa protein in platelets which we believe to be the alpha subunit of a guanine nucleotide-binding regulatory protein or G protein. Based upon our recent studies, this protein has several novel properties. First, it is phosphorylated during platelet activation, apparently by protein kinase C. Second, it is immunologically cross-reactive with G(z-alpha), a putative alpha subunit that has been cloned from two non-platelet cDNA libraries, but not yet isolated. Third, in contrast to the other G proteins which have been a focus for platelet research, it is neither ADP-ribosylated by pertussis toxin nor recognized by antisera that are specific for known pertussis toxin-sensitive G proteins, such as G(i-alpha). Even though G(z- alpha) is not known to be a substrate for protein kinase C, we have provisionally named the platelet protein "G(z-alpha)(plt)" in acknowledgement of the immunologic cross-reactivity of the two proteins. The goal of our studies will be to understand the structure and biology of G(z-alpha)(plt). Specifically, we will: (1) determine the identity of G(z- alpha)(plt) and define its relationship to G(z-alpha), (2) identify the sites at which G(z-alpha)(plt) is phosphorylated, (3) determine the biochemical consequences of phosphorylation and (4) define the role of G(z- alpha)(plt) in platelet function.