Mayer A, Wickner W, Haas A
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire, 03755-3844 USA.
Cell. 1996 Apr 5;85(1):83-94. doi: 10.1016/s0092-8674(00)81084-3.
S. cerevisiae inherits its vacuole by projecting vacuole-derived membrane vesicles and tubules into the bud, where they fuse to establish the daughter vacuole. This homotypic fusion event can be assayed in vitro. It requires Sec17p and Sec18p, the homologs of the mammalian alpha-SNAP and NSF, which cooperate in multiple steps of membrane trafficking. We now report that Sec17p, Sec18p, and ATP are only needed for an early stage of the reaction that results in Sec17p release. Sec17p and Sec18p actions precede, and are needed for, the step employing the Ras-like GTPase Ypt7p. Sec18p-driven release of Sec17p can even precede vacuole docking, as it can occur prior to mixing of vacuoles and is insensitive to vacuole concentration. Sec17p and Sec18p thus may function in a predocking stage of the reaction, rather than in bilayer fusion per se.
酿酒酵母通过将源自液泡的膜泡和小管投射到芽中来继承其液泡，在芽中它们融合以形成子液泡。这种同型融合事件可以在体外进行检测。它需要Sec17p和Sec18p，它们是哺乳动物α-SNAP和NSF的同源物，在膜运输的多个步骤中协同作用。我们现在报告，Sec17p、Sec18p和ATP仅在导致Sec17p释放的反应早期阶段是必需的。Sec17p和Sec18p的作用先于并为使用类Ras GTP酶Ypt7p的步骤所必需。Sec18p驱动的Sec17p释放甚至可以先于液泡对接，因为它可以在液泡混合之前发生并且对液泡浓度不敏感。因此，Sec17p和Sec18p可能在反应的对接前阶段起作用，而不是在双层融合本身中起作用。
