Lowy D R, Willumsen B M
Cancer Surv. 1986;5(2):275-89.
Members of the ras multigene family have been found in virtually all eukaryotes, from yeast to mammals. ras is required for normal cell growth in the yeast Saccharomyces cerevisiae and in at least some mammalian cells. These genes induce tumorigenic transformation of established NIH 3T3 cells by increased expression of a normal ras gene, certain point mutations or amino acid deletion. In tumours, point mutation appears to be the most common mechanism of activation. The ras proteins are found at the plasma membrane, bind guanine nucleotides GDP and GTP and possess a GTPase activity. At least some ras proteins that have been activated by single amino acid substitutions possess a GTPase activity that is lower than that of the normal version. These results are consistent with the hypothesis that ras protein stimulates its putative target(s) when GTP is bound to it, as is true for the G regulatory proteins or elongation factor Tu. In Saccharomyces cerevisiae, ras has been shown to stimulate adenylate cyclase. However, there does not appear to be a direct interaction between ras and adenylate cyclase in mammalian cells.
ras多基因家族的成员几乎在所有真核生物中都有发现，从酵母到哺乳动物。ras对于酿酒酵母和至少一些哺乳动物细胞的正常细胞生长是必需的。这些基因通过正常ras基因的表达增加、某些点突变或氨基酸缺失，诱导已建立的NIH 3T3细胞发生致瘤转化。在肿瘤中，点突变似乎是最常见的激活机制。ras蛋白存在于质膜上，结合鸟嘌呤核苷酸GDP和GTP，并具有GTPase活性。至少一些通过单氨基酸取代激活的ras蛋白具有低于正常版本的GTPase活性。这些结果与以下假设一致：当GTP与其结合时，ras蛋白会刺激其假定的靶标，G调节蛋白或延伸因子Tu也是如此。在酿酒酵母中，ras已被证明可刺激腺苷酸环化酶。然而，在哺乳动物细胞中，ras与腺苷酸环化酶之间似乎没有直接相互作用。
