Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China.
Nat Plants. 2017 Mar 1;3:17011. doi: 10.1038/nplants.2017.11.
Chloroplasts divide by binary fission, which is accomplished by the simultaneous constriction of the FtsZ ring on the stromal side of the inner envelope membrane, and the ARC5 ring on the cytosolic side of the outer envelope membrane. The two rings are connected and coordinated mainly by the interaction between the inner envelope membrane protein ARC6 and the outer envelope membrane protein PDV2 in the intermembrane space. The underlying mechanism of this coordination is unclear to date. Here, we solved the crystal structure of the intermembrane space region of the ARC6-PDV2 complex. The results indicated that PDV2 inserts its carboxy terminus into a pocket formed in ARC6, and this interaction further induces the dimerization of the intermembrane space regions of two ARC6 molecules. A pdv2 mutant attenuating PDV2-induced ARC6 dimerization showed abnormal morphology of ARC6 rings and compromised chloroplast division in plant cells. Together, our data reveal that PDV2-induced dimerization of ARC6 plays a critical role in chloroplast division and provide insights into the coordination mechanism of the internal and external plastid division machineries.
叶绿体通过二分分裂进行分裂，这是通过在内膜的基质侧上的 FtsZ 环和在外膜的胞质侧上的 ARC5 环的同时收缩来完成的。这两个环主要通过内膜蛋白 ARC6 和跨膜空间中外膜蛋白 PDV2 之间的相互作用连接和协调。迄今为止，这种协调的潜在机制尚不清楚。在这里，我们解决了 ARC6-PDV2 复合物的跨膜空间区域的晶体结构。结果表明，PDV2 将其羧基末端插入 ARC6 形成的口袋中，这种相互作用进一步诱导两个 ARC6 分子的跨膜空间区域的二聚化。削弱 PDV2 诱导的 ARC6 二聚化的 pdv2 突变体显示出 ARC6 环的异常形态和植物细胞中叶绿体分裂受损。总之，我们的数据表明 PDV2 诱导的 ARC6 二聚化在叶绿体分裂中起着关键作用，并为内部和外部质体分裂机制的协调机制提供了见解。
