Shibamoto Tadao, Kato Yuki, Watanabe Tadashi
Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan.
FEBS Lett. 2008 Apr 30;582(10):1490-4. doi: 10.1016/j.febslet.2008.03.041. Epub 2008 Apr 7.
The redox potential of cytochrome b559 (Cyt b559) in the D1-D2-Cyt b559 complex from spinach has been determined to be +90+/-2mV vs. SHE at pH 6.0, by thin-layer cell spectroelectrochemistry for the first time. The redox potential, corresponding uniquely to the so-called "low-potential form", exhibited a sigmoidal pH-dependence from pH 4.0 to 9.0, ranging from +115 to +50mV. An analysis of the pH-dependence based on model equations suggests that two histidine residues coordinating to the heme iron in the protein subunits may exert electrostatic influence on the redox potential of Cyt b559.
首次通过薄层电池光谱电化学法测定了菠菜中D1-D2-细胞色素b559（Cyt b559）复合物中细胞色素b559的氧化还原电位，在pH 6.0时相对于标准氢电极（SHE）为+90±2mV。该氧化还原电位唯一对应于所谓的“低电位形式”，在pH 4.0至9.0范围内呈现S形pH依赖性，范围为+115至+50mV。基于模型方程对pH依赖性的分析表明，蛋白质亚基中与血红素铁配位的两个组氨酸残基可能对Cyt b559的氧化还原电位产生静电影响。
