Zentrum für Molekularbiologie der Pflanzen, Entwicklungsgenetik, University of Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany.
Dev Cell. 2012 May 15;22(5):989-1000. doi: 10.1016/j.devcel.2012.03.002.
Intracellular membrane fusion requires complexes of syntaxins with other SNARE proteins and regulatory Sec1/Munc18 (SM) proteins. In membrane fusion mediating, e.g., neurotransmitter release or glucose-stimulated insulin secretion in mammals, SM proteins preferentially interact with the inactive closed, rather than the active open, conformation of syntaxin or with the assembled SNARE complex. Other membrane fusion processes such as vacuolar fusion in yeast involve like membranes carrying cis-SNARE complexes, and the role of SM protein is unknown. We investigated syntaxin-SM protein interaction in membrane fusion of Arabidopsis cytokinesis, which involves cytokinesis-specific syntaxin KNOLLE and SM protein KEULE. KEULE interacted with an open conformation of KNOLLE that complemented both knolle and keule mutants. This interaction occurred at the cell division plane and required the KNOLLE linker sequence between helix Hc and SNARE domain. Our results suggest that in cytokinesis, SM protein stabilizes the fusion-competent open form of syntaxin, thereby promoting trans-SNARE complex formation.
细胞内膜融合需要突触融合蛋白与其他 SNARE 蛋白和调节 Sec1/Munc18（SM）蛋白的复合物。在介导膜融合的过程中，例如哺乳动物中的神经递质释放或葡萄糖刺激的胰岛素分泌，SM 蛋白优先与无活性的封闭构象的突触融合蛋白相互作用，而不是与活性的开放构象的突触融合蛋白相互作用，或者与组装好的 SNARE 复合物相互作用。其他膜融合过程，如酵母中的液泡融合，涉及带有顺式 SNARE 复合物的类似膜，而 SM 蛋白的作用尚不清楚。我们研究了拟南芥胞质分裂中突触融合蛋白与 SM 蛋白的相互作用，该过程涉及胞质分裂特异性突触融合蛋白 KNOLLE 和 SM 蛋白 KEULE。KEULE 与 KNOLLE 的开放构象相互作用，补充了 knolle 和 keule 突变体。这种相互作用发生在细胞分裂平面上，需要 Hc 螺旋和 SNARE 结构域之间的 KNOLLE 连接序列。我们的结果表明，在胞质分裂中，SM 蛋白稳定了融合有活性的开放构象的突触融合蛋白，从而促进了跨 SNARE 复合物的形成。
