Direct Observation of Protonation Reactions during the Catalytic Cycle of Cytochrome c Oxidase

Nyquist, R.; Heitbrink, D.; Bolwien, C.; Heberle, J.; Gennis, R. B.; Wells, T. A.

doi:10.1073/pnas.1530408100

Journal Article

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.FZJ*

2003
Academy Washington, DC

Proceedings of the National Academy of Sciences of the United States of America 100, 8715 - 8720 (2003) [10.1073/pnas.1530408100]

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Please use a persistent id in citations: http://hdl.handle.net/2128/2650 doi:10.1073/pnas.1530408100

Abstract: 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.

Keyword(s): Biophysical Phenomena (MeSH) ; Biophysics (MeSH) ; Carbon Monoxide: chemistry (MeSH) ; Catalysis (MeSH) ; Electron Transport (MeSH) ; Electron Transport Complex IV: chemistry (MeSH) ; Electron Transport Complex IV: genetics (MeSH) ; Electron Transport Complex IV: metabolism (MeSH) ; Glutamic Acid: chemistry (MeSH) ; Models, Molecular (MeSH) ; Mutagenesis, Site-Directed (MeSH) ; Oxidation-Reduction (MeSH) ; Protein Conformation (MeSH) ; Protons (MeSH) ; Rhodobacter sphaeroides: enzymology (MeSH) ; Rhodobacter sphaeroides: genetics (MeSH) ; Spectrophotometry, Infrared (MeSH) ; Protons ; Glutamic Acid ; Carbon Monoxide ; Electron Transport Complex IV ; J ; electron transfer (auto) ; infrared attenuated total reflection (auto) ; membrane protein (auto) ; bacteriorhodopsis (auto) ; glutamic acid (auto)