ARC5, a cytosolic dynamin-like protein from plants, is part of the chloroplast division machinery
ARC5, a cytosolic dynamin-like protein from plants, is part of the chloroplast division machinery
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DOI：
10.1073/pnas.0530206100
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发表时间：
2003-04-01
影响因子：
11.1
通讯作者：
Osteryoung, KW
中科院分区：
文献类型：
--
作者：
Gao, HB;Kadirjan-Kalbach, D;Osteryoung, KW
植物细胞中的叶绿体分裂是由一个复杂的大分子机器协调进行的，其组件位于被膜的内外表面。到目前为止，唯一被鉴定的叶绿体分裂蛋白是来自内共生的，并且定位于细胞器内。利用拟南芥中的定位克隆方法，结合一种新的定位突变位点的策略，我们已经鉴定了一个编码新的叶绿体分裂蛋白ARC5的基因。ARC5的突变体表现出叶绿体收缩缺陷，叶绿体变大，呈哑铃状，并被野生型ARC5拯救。ARC5基因产物与GTP酶的Dynamin家族有相似之处，后者介导真核生物的内吞作用、线粒体分裂和其他细胞器的分裂和融合事件。系统发育分析表明，ARC5与一组植物特有的动力素样蛋白有关。GFP-ARC5融合蛋白定位于叶绿体分裂部位的环状结构。叶绿体输入和蛋白酶保护分析表明，ARC5环位于叶绿体的外表面。因此，ARC5是第一个被鉴定的叶绿体分裂复合体的胞质组分。ARC5在原核生物中没有明显的对应物，这表明它是从植物的真核祖先中存在的一种动力蛋白相关蛋白进化而来的。这些结果表明，叶绿体分裂装置是混合进化起源的，它与细菌的细胞分裂机制和真核生物的动力蛋白介导的细胞器分裂机制在结构和机制上都有相似之处。
Chloroplast division in plant cells is orchestrated by a complex macromolecular machine with components positioned on both the inner and outer envelope surfaces. The only plastid division proteins identified to date are of endosymbiotic origin and are localized inside the organelle. Employing positional cloning methods in Arabidopsis in conjunction with a novel strategy for pinpointing the mutant locus, we have identified a gene encoding a new chloroplast division protein, ARC5. Mutants of ARC5 exhibit defects in chloroplast constriction, have enlarged, dumbbell-shaped chloroplasts, and are rescued by a wild-type copy of ARC5. The ARC5 gene product shares similarity with the dynamin family of GTPases, which mediate endocytosis, mitochondrial division, and other organellar fission and fusion events in eukaryotes. Phylogenetic analysis showed that ARC5 is related to a group of dynamin-like proteins unique to plants. A GFP-ARC5 fusion protein localizes to a ring at the chloroplast division site. Chloroplast import and protease protection assays indicate that the ARC5 ring is positioned on the outer surface of the chloroplast. Thus, ARC5 is the first cytosolic component of the chloroplast division complex to be identified. ARC5 has no obvious counterparts in prokaryotes, suggesting that it evolved from a dynamin-related protein present in the eukaryotic ancestor of plants. These results indicate that the chloroplast division apparatus is of mixed evolutionary origin and that it shares structural and mechanistic similarities with both the cell division machinery of bacteria and the dynamin-mediated organellar fission machineries of eukaryotes.