Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, PB 65 (Viikinkaari 1), FI-00014, Helsinki, Finland.
Proc Natl Acad Sci U S A. 2010 Oct 26;107(43):18469-74. doi: 10.1073/pnas.1010974107. Epub 2010 Oct 11.
Cytochrome c oxidase is the terminal enzyme of the respiratory chain that is responsible for biological energy conversion in mitochondria and aerobic bacteria. The membrane-bound enzyme converts free energy from oxygen reduction to an electrochemical proton gradient by functioning as a redox-coupled proton pump. Although the 3D structure and functional studies have revealed proton conducting pathways in the enzyme interior, the location of proton donor and acceptor groups are not fully identified. We show here by time-resolved optical and FTIR spectroscopy combined with time-resolved electrometry that some mutant enzymes incapable of proton pumping nevertheless initiate catalysis by proton transfer to a proton-loading site. A conserved tyrosine in the so-called D-channel is identified as a potential proton donor that determines the efficiency of this reaction.
细胞色素 c 氧化酶是呼吸链的末端酶，负责线粒体和需氧细菌中的生物能量转换。这种膜结合酶通过充当氧化还原偶联质子泵，将来自氧还原的自由能转化为电化学质子梯度。尽管三维结构和功能研究已经揭示了酶内部的质子传导途径，但质子供体和受体基团的位置尚未完全确定。我们通过时间分辨光学和傅里叶变换红外光谱结合时间分辨电化学表明，一些不能进行质子泵的突变酶仍然可以通过质子转移到质子加载位点来启动催化作用。在所谓的 D 通道中保守的酪氨酸被鉴定为潜在的质子供体，它决定了该反应的效率。
