Chen Yong, Shin Yeon-Kyun, Bassham Diane C
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
J Mol Biol. 2005 Jul 1;350(1):92-101. doi: 10.1016/j.jmb.2005.04.061.
SNARE complex formation is essential for membrane fusion in exocytotic and vacuolar trafficking pathways. Vesicle-associated (v-) SNARE associates with a target membrane (t-) SNARE to form a SNARE complex bridging two membranes, which may facilitate membrane fusion. The Arabidopsis genome encodes a large number of predicted SNARE proteins that might function primarily as fusogens for vesicle transport in endomembrane systems. The SNAREs SYP41, SYP61 and VTI12 reside in the trans-Golgi network and have been proposed to function together in vesicle fusion with this organelle. Here, we use a liposome fusion assay to demonstrate that VTI12 and either SYP41 or SYP61, but not both, are required for membrane fusion. This indicates that SYP41 and SYP61 are likely to function in independent vesicle fusion reactions in Arabidopsis. In addition, we have identified two new functionally interchangeable components, YKT61 and YKT62, that show sequence similarity to the multifunctional yeast SNARE YKT6. Both YKT61 and YKT62 interact with SYP41 and are essential for membrane fusion mediated by either SYP41 or SYP61. These results therefore define the core constituents required for membrane fusion at the Arabidopsis trans-Golgi network.
SNARE复合体的形成对于胞吐作用和液泡运输途径中的膜融合至关重要。囊泡相关（v-）SNARE与靶膜（t-）SNARE结合，形成连接两个膜的SNARE复合体，这可能促进膜融合。拟南芥基因组编码大量预测的SNARE蛋白，它们可能主要作为内膜系统中囊泡运输的融合蛋白发挥作用。SNARE蛋白SYP41、SYP61和VTI12位于反式高尔基体网络中，有人提出它们在与该细胞器的囊泡融合中共同发挥作用。在这里，我们使用脂质体融合试验来证明膜融合需要VTI12与SYP41或SYP61之一（而非两者）。这表明SYP41和SYP61可能在拟南芥独立的囊泡融合反应中发挥作用。此外，我们鉴定出两个新的功能可互换成分YKT61和YKT62，它们与多功能酵母SNARE YKT6具有序列相似性。YKT61和YKT62都与SYP41相互作用，并且对于由SYP41或SYP61介导的膜融合至关重要。因此，这些结果确定了拟南芥反式高尔基体网络处膜融合所需的核心成分。
