Daniel J, Bush J, Cardelli J, Spiegelman G B, Weeks G
Department of Microbiology, University of British Columbia, Vancouver, Canada.
Oncogene. 1994 Feb;9(2):501-8.
In Dictyostelium discoideum, three ras genes (rasD, rasG and rasB) and one ras-related gene (rap1) have been previously isolated and characterized, and the deduced amino acid sequence of their predicted protein products share at least 50% sequence identity with the human H-Ras protein. We have now cloned and characterized two additional members of the ras gene subfamily in Dictyostelium, rasC and rasS. These genes are developmentally regulated and unlike the previously isolated Dictyostelium ras genes, maximum levels of their transcripts were detected during aggregation, suggesting that the encoded proteins have distinct functions during aggregation. The rasC cDNA encodes a 189 amino acid protein that is 65% identical to the Dictyostelium RasD and RasG proteins and 56% identical to the human H-Ras protein. The predicted 194 amino acid gene product encoded by rasS is 60% identical to the Dictyostelium RasD and RasG proteins and 54% identical to the human H-Ras protein. Whereas RasD, RasG, RasB and Rap1 are totally conserved in their putative effector domains relative to H-Ras, RasC and RasS have single amino acid substitutions in their effector domains, consistent with the idea that they have unique functions. In RasC, aspartic acid-38 has been replaced by asparagine (D38N), and in RasS, isoleucine-36 has been replaced by leucine (I36L). In addition, both proteins have several differences in the effector-proximal domain, a domain which is believed to play a role in Ras target activation. In RasC, there is a single conservative amino acid change in the canonical sequence of the binding site for the Ras-specific monoclonal antibody Y13-259, and consequently, RasC is less immunoreactive with the antibody than either of the Dictyostelium RasD or RasG proteins. In contrast, RasS, which has three substitutions in the Y13-259 binding site, does not react with the Y13-259 antibody.
在盘基网柄菌中，先前已分离并鉴定出三个ras基因（rasD、rasG和rasB）以及一个ras相关基因（rap1），其预测的蛋白质产物的推导氨基酸序列与人类H-Ras蛋白的序列同一性至少为50%。我们现在已经克隆并鉴定了盘基网柄菌中ras基因亚家族的另外两个成员，rasC和rasS。这些基因受到发育调控，与先前分离的盘基网柄菌ras基因不同，在聚集过程中检测到它们转录本的最高水平，这表明编码的蛋白质在聚集过程中具有不同的功能。rasC cDNA编码一种189个氨基酸的蛋白质，与盘基网柄菌的RasD和RasG蛋白的同一性为65%，与人类H-Ras蛋白的同一性为56%。rasS预测的194个氨基酸的基因产物与盘基网柄菌的RasD和RasG蛋白的同一性为60%，与人类H-Ras蛋白的同一性为54%。相对于H-Ras，RasD、RasG、RasB和Rap1在其假定的效应结构域中完全保守，而RasC和RasS在其效应结构域中有单个氨基酸取代，这与它们具有独特功能的观点一致。在RasC中，天冬氨酸-38被天冬酰胺取代（D38N），在RasS中，异亮氨酸-36被亮氨酸取代（I36L）。此外，这两种蛋白质在效应器近端结构域也有几个差异，该结构域被认为在Ras靶点激活中起作用。在RasC中，Ras特异性单克隆抗体Y13-259结合位点的经典序列中有一个保守的氨基酸变化，因此，RasC与该抗体的免疫反应性低于盘基网柄菌的RasD或RasG蛋白。相比之下，在Y13-259结合位点有三个取代的RasS不与Y13-259抗体反应。
