Ries Fabian, Herkt Claudia, Willmund Felix
Molecular Genetics of Eukaryotes, University of Kaiserslautern, Paul-Ehrlich-Strasse 23, 67663 Kaiserslautern, Germany.
Plants (Basel). 2020 Feb 7;9(2):214. doi: 10.3390/plants9020214.
Cells depend on the continuous renewal of their proteome composition during the cell cycle and in order to replace aberrant proteins or to react to changing environmental conditions. In higher eukaryotes, protein synthesis is achieved by up to five million ribosomes per cell. With the fast kinetics of translation, the large number of newly made proteins generates a substantial burden for protein homeostasis and requires a highly orchestrated cascade of factors promoting folding, sorting and final maturation. Several of the involved factors directly bind to translating ribosomes for the early processing of emerging nascent polypeptides and the translocation of ribosome nascent chain complexes to target membranes. In plant cells, protein synthesis also occurs in chloroplasts serving the expression of a relatively small set of 60-100 protein-coding genes. However, most of these proteins, together with nucleus-derived subunits, form central complexes majorly involved in the essential processes of photosynthetic light reaction, carbon fixation, metabolism and gene expression. Biogenesis of these heterogenic complexes adds an additional level of complexity for protein biogenesis. In this review, we summarize the current knowledge about co-translationally binding factors in chloroplasts and discuss their role in protein folding and ribosome translocation to thylakoid membranes.
细胞在细胞周期中以及为了替换异常蛋白质或应对不断变化的环境条件，依赖于其蛋白质组组成的持续更新。在高等真核生物中，每个细胞多达五百万个核糖体进行蛋白质合成。由于翻译的快速动力学，大量新合成的蛋白质给蛋白质稳态带来了巨大负担，需要一系列高度协调的因子来促进折叠、分选和最终成熟。一些相关因子直接结合到正在翻译的核糖体上，用于新生多肽的早期加工以及核糖体新生链复合物向靶膜的转运。在植物细胞中，蛋白质合成也发生在叶绿体中，用于表达一组相对较少的60 - 100个蛋白质编码基因。然而，这些蛋白质中的大多数与细胞核来源的亚基一起，形成主要参与光合光反应、碳固定、代谢和基因表达等基本过程的核心复合物。这些异源复合物的生物发生为蛋白质生物合成增加了额外的复杂性。在本综述中，我们总结了目前关于叶绿体中共翻译结合因子 的知识，并讨论了它们在蛋白质折叠和核糖体向类囊体膜转运中的作用。
