Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States.
Elife. 2020 Jan 21;9:e53559. doi: 10.7554/eLife.53559.
Yeast vacuole fusion requires R-SNARE, Q-SNAREs, and HOPS. A HOPS SM-family subunit binds the R- and Qa-SNAREs. We now report that HOPS binds each of the four SNAREs. HOPS catalyzes fusion when the Q-SNAREs are not pre-assembled, ushering them into a functional complex. Co-incubation of HOPS, proteoliposomes bearing R-SNARE, and proteoliposomes with any two Q-SNAREs yields a rapid-fusion complex with 3 SNAREs in a -assembly. The missing Q-SNARE then induces sudden fusion. HOPS can 'template' SNARE complex assembly through SM recognition of R- and Qa-SNAREs. Though the Qa-SNARE is essential for spontaneous SNARE assembly, HOPS also assembles a rapid-fusion complex between R- and QbQc-SNARE proteoliposomes in the absence of Qa-SNARE, awaiting Qa for fusion. HOPS-dependent fusion is saturable at low concentrations of each Q-SNARE, showing binding site functionality. HOPS thus tethers membranes and recognizes each SNARE, assembling R+Qa or R+QbQc rapid fusion intermediates.
酵母液泡融合需要 R-SNARE、Q-SNARE 和 HOPS。HOPS SM 家族亚基结合 R- 和 Qa-SNARE。我们现在报告 HOPS 结合了四个 SNARE 中的每一个。当 Q-SNARE 未预先组装时，HOPS 会催化融合，将其引入功能复合物。HOPS、带有 R-SNARE 的质体和带有任何两个 Q-SNARE 的质体共孵育会产生一个快速融合复合物，其中 3 个 SNARE 在 - 装配中。然后缺失的 Q-SNARE 会诱导突然融合。HOPS 可以通过 SM 识别 R- 和 Qa-SNARE 来“模板”SNARE 复合物组装。尽管 Qa-SNARE 对于自发 SNARE 组装是必不可少的，但 HOPS 也可以在没有 Qa-SNARE 的情况下组装 R- 和 QbQc-SNARE 质体之间的快速融合复合物，等待 Qa 进行融合。HOPS 依赖性融合在每种 Q-SNARE 的低浓度下是饱和的，显示出结合位点的功能。因此，HOPS 可以连接膜并识别每个 SNARE，组装 R+Qa 或 R+QbQc 快速融合中间产物。
