Osyczka A, Nagashima K V, Sogabe S, Miki K, Shimada K, Matsuura K
Department of Biology, Tokyo Metropolitan University, Minamiohsawa 1-1, Hachioji, Tokyo 192-0397, Japan.
J Biol Chem. 2001 Jun 29;276(26):24108-12. doi: 10.1074/jbc.M101141200. Epub 2001 Apr 19.
The tetraheme cytochrome subunits of the photosynthetic reaction centers (RCs) in two species of purple bacteria, Rubrivivax gelatinosus and Blastochloris (Rhodopseudomonas) viridis, were compared in terms of their capabilities to bind different electron-donor proteins. The wild-type RCs from both species and mutated forms of R. gelatinosus RCs (with amino acid substitutions introduced to the binding domain for electron-donor proteins) were tested for their reactivity with soluble cytochromes and high potential iron-sulfur protein. Cytochromes from both species were good electron donors to the B. viridis RC and the R. gelatinosus RC. The reactivity in the R. gelatinosus RC showed a clear dependence on the polarity of the charges introduced to the binding domain, indicating the importance of the electrostatic interactions. In contrast, high potential iron-sulfur protein, presumed to operate according to the hydrophobic mechanism of binding, reacted significantly only with the R. gelatinosus RC. Evolutionary substitution of amino acids in a region of the binding domain on the cytochrome subunit surface probably caused the change in the principal mode of protein-protein interactions in the electron-transfer chains.
对两种紫色细菌——胶质红假单胞菌和绿脓红假单胞菌（以前称为绿脓红假单胞菌）光合反应中心（RC）的四血红素细胞色素亚基结合不同电子供体蛋白的能力进行了比较。测试了这两个物种的野生型RC以及胶质红假单胞菌RC的突变形式（在电子供体蛋白的结合结构域引入了氨基酸替换）与可溶性细胞色素和高电位铁硫蛋白的反应活性。来自这两个物种的细胞色素都是绿脓红假单胞菌RC和胶质红假单胞菌RC的良好电子供体。胶质红假单胞菌RC中的反应活性明显依赖于引入结合结构域的电荷极性，表明静电相互作用的重要性。相比之下，推测通过疏水结合机制起作用的高电位铁硫蛋白仅与胶质红假单胞菌RC有显著反应。细胞色素亚基表面结合结构域区域氨基酸的进化替代可能导致了电子传递链中蛋白质-蛋白质相互作用主要模式的变化。
