Murcha Monika W, Kmiec Beata, Kubiszewski-Jakubiak Szymon, Teixeira Pedro F, Glaser Elzbieta, Whelan James
Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-10691 Stockholm, Sweden.
J Exp Bot. 2014 Dec;65(22):6301-35. doi: 10.1093/jxb/eru399. Epub 2014 Oct 16.
The majority of more than 1000 proteins present in mitochondria are imported from nuclear-encoded, cytosolically synthesized precursor proteins. This impressive feat of transport and sorting is achieved by the combined action of targeting signals on mitochondrial proteins and the mitochondrial protein import apparatus. The mitochondrial protein import apparatus is composed of a number of multi-subunit protein complexes that recognize, translocate, and assemble mitochondrial proteins into functional complexes. While the core subunits involved in mitochondrial protein import are well conserved across wide phylogenetic gaps, the accessory subunits of these complexes differ in identity and/or function when plants are compared with Saccharomyces cerevisiae (yeast), the model system for mitochondrial protein import. These differences include distinct protein import receptors in plants, different mechanistic operation of the intermembrane protein import system, the location and activity of peptidases, the function of inner-membrane translocases in linking the outer and inner membrane, and the association/regulation of mitochondrial protein import complexes with components of the respiratory chain. Additionally, plant mitochondria share proteins with plastids, i.e. dual-targeted proteins. Also, the developmental and cell-specific nature of mitochondrial biogenesis is an aspect not observed in single-celled systems that is readily apparent in studies in plants. This means that plants provide a valuable model system to study the various regulatory processes associated with protein import and mitochondrial biogenesis.
线粒体中存在的1000多种蛋白质，大部分是从核编码、在细胞质中合成的前体蛋白导入的。这种令人印象深刻的运输和分选过程是通过线粒体蛋白上的靶向信号与线粒体蛋白导入装置的共同作用实现的。线粒体蛋白导入装置由许多多亚基蛋白复合物组成，这些复合物识别、转运线粒体蛋白并将其组装成功能复合物。虽然参与线粒体蛋白导入的核心亚基在广泛的系统发育间隔中高度保守，但与线粒体蛋白导入的模型系统酿酒酵母（酵母）相比，这些复合物的辅助亚基在身份和/或功能上存在差异。这些差异包括植物中独特的蛋白导入受体、膜间蛋白导入系统不同的机制操作、肽酶的位置和活性、内膜转位酶在连接外膜和内膜中的功能，以及线粒体蛋白导入复合物与呼吸链成分的关联/调节。此外，植物线粒体与质体共享蛋白质，即双靶向蛋白。而且，线粒体生物发生的发育和细胞特异性本质是单细胞系统中未观察到的一个方面，在植物研究中很容易显现出来。这意味着植物为研究与蛋白导入和线粒体生物发生相关的各种调控过程提供了一个有价值的模型系统。
