Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Curr Opin Cell Biol. 2010 Aug;22(4):447-53. doi: 10.1016/j.ceb.2010.04.003. Epub 2010 May 1.
The small GTPase Sar1 resides at the core of a regulatory cycle that controls protein export from the ER in COPII vesicles. Recent advances in minimally reconstituted systems indicate continual flux of Sar1 through GTPase cycles facilitates cargo concentration into forming vesicles that ultimately bud from membranes. During export from ER membranes, this GTPase cycle is harnessed through the combinatorial power of multiple coat subunits and cargo adaptors to sort an expanding array of proteins into ER-derived vesicles. The COPII budding machinery is further organized into higher-order structures at transitional zones on the ER surface where the large multi-domain Sec16 protein appears to perform a central function.
小分子 GTP 酶 Sar1 位于控制内质网中 COPII 小泡中蛋白质输出的调节循环的核心。最小重组成分系统的最新进展表明，Sar1 通过 GTP 酶循环的持续流动有助于将货物浓缩到形成小泡中，最终从小泡中出芽。在从内质网膜中输出过程中，这个 GTP 酶循环通过多个外壳亚基和货物衔接蛋白的组合能力被利用，以将不断扩展的蛋白质种类分拣到内质网衍生的小泡中。COPII 出芽机制进一步在内质网表面的过渡区组织成更高阶的结构，其中大型多结构域 Sec16 蛋白似乎发挥了核心功能。
