Molina y Vedia L, Ohmstede C A, Lapetina E G
Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, NC 27709.
Biochem Biophys Res Commun. 1990 Aug 31;171(1):319-24. doi: 10.1016/0006-291x(90)91395-9.
Rap-2B is a novel ras-related protein that is 89% identical to rap-2 at the amino acid level. Based on its amino acid sequence, it is anticipated that rap-2B binds guanine nucleotides. Here we show that purified, bacterially expressed rap-2B does bind both GTP and GDP in a Mg2(+)-dependent fashion. The relative affinity of rap-2B for GTP is higher than that for GDP, both at low and high concentrations of Mg2+. This contrasts with N-ras p21 and could be of functional significance. Moreover, a polyclonal antiserum was raised against the recombinant rap-2B protein purified from E. coli lysates. This antiserum recognized a major protein of Mr approximately 21000 on Western blots of platelet membrane proteins, and immunoprecipitates rap-2B complexed with GTP or GDP.
Rap-2B是一种新型的与ras相关的蛋白质，在氨基酸水平上与rap-2有89%的同源性。根据其氨基酸序列，预计rap-2B能结合鸟嘌呤核苷酸。在此我们表明，经细菌表达并纯化的rap-2B确实能以Mg2(+)依赖的方式结合GTP和GDP。在低浓度和高浓度Mg2+条件下，rap-2B对GTP的相对亲和力均高于对GDP的亲和力。这与N-ras p21不同，可能具有功能上的重要意义。此外，我们制备了针对从大肠杆菌裂解物中纯化的重组rap-2B蛋白的多克隆抗血清。该抗血清在血小板膜蛋白的Western印迹中识别出一条分子量约为21000的主要蛋白条带，并能免疫沉淀与GTP或GDP结合的rap-2B复合物。
