Structural Basis for Electron Transfer Between the BacterialReaction Center and Cytochrome c2 in Rhodobacter Sphaeroide studied by Site Directed Mutagenesis

光合细菌通过称为反应中心（RC）的色素蛋白复合体中的光诱导电子转移反应将光能转化为化学能。RC内的初始电荷分离与通过移动电子载体细胞色素c2的电子转移而跨越膜的电子转移相耦合。RC与细胞色素c2反应的重要特征是高电子转移率和对电子转移伙伴的分子识别。这两种性质的结构基础将通过研究突变以下类型残基的影响来研究：(1)RC和细胞色素上的带电残基将被修饰，以研究两个氧化还原伙伴之间的静电相互作用。在RC（负电荷到正电荷残基）和细胞色素（负电荷到正电荷残基）上的互补电荷变化将绘制出细胞色素RC复合物中特定的离子配对相互作用。(2) RC表面靠近细胞色素结合位点的不带电残基会突变为具有不同分子大小和疏水性的残基。观察到的结合和电子转移的变化模式将用于绘制结合相互作用和电子转移的可能途径。生物系统的大部分能量来自于生物膜中蛋白质之间的电子转移。电子转移的两个主要问题目前还不清楚：电子供体和受体蛋白质是如何相互识别和结合的？电子通过蛋白质传递的途径是什么？这两个问题的答案将在光合细菌Rb的细菌反应中心和细胞色素c2之间的反应中得到研究。sphaeroides。* * *

9304782 Okamura Photosynthetic bacteria convert light energy into chemical energy by photo-induced electron transfer reactions in a pigment protein complex called the reaction center (RC). The initial charge separation within the RC is coupled to electron transfer across the membrane by electron transfer from a mobile electron carrier, cytochrome c2. Important features of the reaction between the RC and cytochrome c2 are the high rate of electron transfer and also the molecular recognition of electron transfer partners. The structural basis for these two properties will be investigated by studying the effects of mutating the following types of residues: (1) Charged residues on the RC and cytochrome will be modified to investigate electrostatic interactions between the two redox partners. Complementary charge changes on the RC (negative to positive charged residues) and cytochrome (negative to positive charged residues) will be made to map out the specific ion pairing interactions in the cytochrome RC complex. (2) Uncharged residues on the RC surface near the cytochrome binding site will be mutated to residues having different molecular sizes and hydrophobicity. The pattern of changes in binding and electron transfer observed will be used to map out the binding interaction and possible pathways for electron transfer. %%% Biological systems derive much of their energy from electron transfer between proteins in biological membranes. Two major questions of electron transfer that are currently not understood are: How do electron donor and acceptor proteins recognize and bind to each other? and what is the pathway for electron transfer though proteins? The answers to both of these questions will be studied for the reaction between the bacterial reaction center and cytochrome c2, from the photosynthetic bacterium Rb. sphaeroides. ***