Ungermann C, Wickner W
Dartmouth Medical School, Department of Biochemistry, Hanover, NH 03755, USA.
EMBO J. 1998 Jun 15;17(12):3269-76. doi: 10.1093/emboj/17.12.3269.
The vacuole v-t-SNARE complex is disassembled by Sec17p/alpha-SNAP and Sec18p/NSF prior to vacuole docking and fusion. We now report a functional characterization of the vacuolar SNARE Vam7p, a SNAP-25 homolog. Although Vam7p has no hydrophobic domains, it is tightly associated with the vacuolar membrane. Vam7p is a constituent of the vacuole SNARE complex and is released from this complex by the Sec17p/Sec18p/ATP-mediated priming of the vacuoles. Even in the absence of the vacuolar v-SNARE Nyv1p, a subcomplex which includes Vam7p and the t-SNARE Vam3p is preserved. Vam7p is necessary for the stability of the vacuolar SNARE complex, since vacuoles from mutants deleted in VAM7 do not have a Vam3p-Nyv1p complex. Furthermore, Vam7p alone, in the absence of Nyv1p and Vam3p, cannot mediate fusion with wild-type vacuoles, whereas vacuoles with only Nyv1p or Vam3p alone can fuse with wild-type vacuoles in the absence of the other two SNAREs. Thus, Vam7p is important for the stable assembly and efficient function of the vacuolar SNARE complex and maintenance of the vacuolar morphology. This functional characterization of Vam7p suggests a general role for SNAP-25 homologs, not only on the plasma membrane but along the secretory pathway.
在液泡对接和融合之前，液泡v - t - SNARE复合体被Sec17p/α - SNAP和Sec18p/NSF拆解。我们现在报告了液泡SNARE蛋白Vam7p（一种SNAP - 25同源物）的功能特性。尽管Vam7p没有疏水结构域，但它与液泡膜紧密相连。Vam7p是液泡SNARE复合体的一个组成部分，并且通过Sec17p/Sec18p/ATP介导的液泡引发作用从该复合体中释放出来。即使在没有液泡v - SNARE Nyv1p的情况下，一个包含Vam7p和t - SNARE Vam3p的亚复合体仍然存在。Vam7p对于液泡SNARE复合体的稳定性是必需的，因为缺失VAM7的突变体的液泡没有Vam3p - Nyv1p复合体。此外，在没有Nyv1p和Vam3p的情况下，单独的Vam7p不能介导与野生型液泡的融合，而仅含有Nyv1p或Vam3p的液泡在没有其他两种SNARE的情况下可以与野生型液泡融合。因此，Vam7p对于液泡SNARE复合体的稳定组装和高效功能以及液泡形态的维持很重要。Vam7p的这种功能特性表明SNAP - 25同源物不仅在质膜上，而且在整个分泌途径中都发挥着普遍作用。
