This title appears in the Scientific Report : 2003 

Direct Observation of Protonation Reactions during the Catalytic Cycle of Cytochrome c Oxidase
Nyquist, R.
Heitbrink, D. / Bolwien, C. / Wells, T. A. / Gennis, R. B. / Heberle, J.
Biologische Strukturforschung; IBI-2
Proceedings of the National Academy of Sciences of the United States of America, 100 (2003) S. 8715 - 8720
Washington, DC Academy 2003
8715 - 8720
Journal Article
Proceedings of the National Academy of Sciences of the United States of America 100
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Cytochrome c oxidase, the terminal protein in the respiratory chain, converts oxygen into water and helps generate the electrochemical gradient used in the synthesis of ATP. The catalytic action of cytochrome c oxidase involves electron transfer, proton transfer, and O2 reduction. These events trigger specific molecular changes at the active site, which, in turn, influence changes throughout the protein, including alterations of amino acid side chain orientations, hydrogen bond patterns, and protonation states. We have used IR difference spectroscopy to investigate such modulations for the functional intermediate states E, R2,Pm, and F. These spectra reveal deprotonation of its key glutamic acid E286 in the E and in the Pm states. The consecutive deprotonation and reprotonation of E286 twice within one catalytic turnover illustrates the role of this residue as a proton shuttle. In addition, the spectra point toward deprotonation of a redox-active tyrosine, plausibly Y288, in the F intermediate. Structural insights into the molecular mechanism of catalysis based on the subtle molecular changes observed with IR difference spectroscopy are discussed.