Brennwald P, Novick P
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Nature. 1993 Apr 8;362(6420):560-3. doi: 10.1038/362560a0.
The genes SEC4 and YPT1 encode Ras-related GTP-binding proteins in the yeast Saccharomyces cerevisiae. Ypt1 is necessary for vesicular transport from the endoplasmic reticulum to the Golgi, whereas Sec4 is required for fusion of post-Golgi secretory vesicles to the plasma membrane. Recently, three structural domains have been proposed to specify the stage in cellular transport at which members of the Sec4/Ypt1/Rab family act: the effector domain, the C-terminal hypervariable region, and a region corresponding to loop 7 in the structure of p21ras (ref. 8). Here we use Sec4/Ypt1 chimaeras to show that these three regions cooperate to specify Ypt1 function and that the C-terminal hypervariable region is needed for Ypt1 localization to the Golgi. Unexpectedly, we found that a single chimaera can function as either Ypt1 or Sec4 without missorting carboxypeptidase Y or invertase.
基因SEC4和YPT1在酿酒酵母中编码与Ras相关的GTP结合蛋白。Ypt1对于从内质网到高尔基体的囊泡运输是必需的，而Sec4对于高尔基体后分泌囊泡与质膜的融合是必需的。最近，有人提出三个结构域来确定Sec4/Ypt1/Rab家族成员在细胞运输中发挥作用的阶段：效应结构域、C末端高变区以及与p21ras结构中第7环相对应的区域（参考文献8）。在这里，我们使用Sec4/Ypt1嵌合体来表明这三个区域共同作用以确定Ypt1的功能，并且C末端高变区是Ypt1定位于高尔基体所必需的。出乎意料的是，我们发现单个嵌合体可以作为Ypt1或Sec4发挥作用，而不会使羧肽酶Y或转化酶发生错误分选。
