Kim Ju Yaen, Nakayama Masato, Toyota Hiroshi, Kurisu Genji, Hase Toshiharu
Division of Protein Chemistry and.
Division of Protein Structural Biology, Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
J Biochem. 2016 Aug;160(2):101-9. doi: 10.1093/jb/mvw016. Epub 2016 Feb 26.
The structure of the complex of maize sulfite reductase (SiR) and ferredoxin (Fd) has been determined by X-ray crystallography. Co-crystals of the two proteins prepared under different conditions were subjected to the diffraction analysis and three possible structures of the complex were solved. Although topological relationship of SiR and Fd varied in each of the structures, two characteristics common to all structures were found in the pattern of protein-protein interactions and positional arrangements of redox centres; (i) a few negative residues of Fd contact with a narrow area of SiR with positive electrostatic surface potential and (ii) [2Fe-2S] cluster of Fd and [4Fe-4S] cluster of SiR are in a close proximity with the shortest distance around 12 Å. Mutational analysis of a total of seven basic residues of SiR distributed widely at the interface of the complex showed their importance for supporting an efficient Fd-dependent activity and a strong physical binding to Fd. These combined results suggest that the productive electron transfer complex of SiR and Fd could be formed through multiple processes of the electrostatic intermolecular interaction and this implication is discussed in terms of the multi-functionality of Fd in various redox metabolisms.
通过X射线晶体学确定了玉米亚硫酸还原酶（SiR）和铁氧还蛋白（Fd）复合物的结构。对在不同条件下制备的两种蛋白质的共晶体进行衍射分析，解析出了该复合物的三种可能结构。尽管每种结构中SiR和Fd的拓扑关系各不相同，但在蛋白质-蛋白质相互作用模式和氧化还原中心的位置排列方面发现了所有结构共有的两个特征：（i）Fd的一些带负电残基与SiR带正电表面电位的狭窄区域接触；（ii）Fd的[2Fe-2S]簇和SiR的[4Fe-4S]簇紧密相邻，最短距离约为12 Å。对广泛分布于复合物界面的SiR总共七个碱性残基进行突变分析，结果表明它们对于支持高效的Fd依赖性活性以及与Fd的强物理结合至关重要。这些综合结果表明，SiR和Fd的有效电子转移复合物可能通过静电分子间相互作用的多个过程形成，并且根据Fd在各种氧化还原代谢中的多功能性对这一观点进行了讨论。
