Institute of Microbiology and Genetics, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany.
FEBS J. 2011 Nov;278(22):4179-88. doi: 10.1111/j.1742-4658.2011.08374.x. Epub 2011 Oct 20.
Organisms employ one of several different enzyme systems to mature cytochromes c. The biosynthetic process involves the periplasmic reduction of cysteine residues in the heme c attachment motif of the apocytochrome, transmembrane transport of heme b and stereospecific covalent heme attachment via thioether bonds. The biogenesis System II (or Ccs system) is employed by β-, δ- and ε-proteobacteria, Gram-positive bacteria, Aquificales and cyanobacteria, as well as by algal and plant chloroplasts. System II comprises four (sometimes only three) membrane-bound proteins: CcsA (or ResC) and CcsB (ResB) are the components of the cytochrome c synthase, whereas CcdA and CcsX (ResA) function in the generation of a reduced heme c attachment motif. Some ε-proteobacteria contain CcsBA fusion proteins constituting single polypeptide cytochrome c synthases especially amenable for functional studies. This minireview highlights the recent findings on the structure, function and specificity of individual System II components and outlines the future challenges that remain to our understanding of the fascinating post-translational protein maturation process in more detail.
生物体会利用几种不同的酶系统来成熟细胞色素 c。生物合成过程涉及在脱细胞色素的血红素 c 附着基序中半胱氨酸残基的周质还原、血红素 b 的跨膜转运以及通过硫醚键的立体特异性共价血红素附着。系统 II（或 Ccs 系统）由β-、δ-和ε-变形菌、革兰氏阳性菌、Aquificales 和蓝藻以及藻类和植物叶绿体使用。系统 II 由四个（有时只有三个）膜结合蛋白组成：CcsA（或 ResC）和 CcsB（ResB）是细胞色素 c 合酶的组成部分，而 CcdA 和 CcsX（ResA）则在还原血红素 c 附着基序的生成中发挥作用。一些ε-变形菌含有 CcsBA 融合蛋白，构成单一多肽细胞色素 c 合酶，特别适合功能研究。这篇综述强调了关于单个系统 II 成分的结构、功能和特异性的最新发现，并概述了在更详细地了解迷人的翻译后蛋白成熟过程方面仍然存在的未来挑战。
