title: Time-resolved ATR-FTIR spectroscopy of the oxygen reaction in the D124N mutant of cytochrome c oxidase from Paracoccus denitrificans.
abstract: Real-time measurements of the cytochrome c oxidase reaction with oxygen were performed by ATR-FTIR spectroscopy, using a mutant with a blocked D-pathway of proton transfer (D124N, Paracoccus denitrificans numbering). The complex spectrum of the ferryl-->oxidized transition together with other bands showed protonation of Glu 278 with a peak position at 1743 cm-1. Since our time resolution was not sufficient to follow the earlier reaction steps, the FTIR spectrum of the CO-inhibited fully reduced-->ferryl transition was obtained as a difference between the spectrum before the laser flash and the first spectrum after it. A trough at 1735 cm-1 due to deprotonation of Glu 278 was detected in this spectrum. These observations confirm the proposal [Smirnova I.A., et al. (1999) Biochemistry 38, 6826-6833] that the proton required for chemistry at the binuclear site is taken from Glu 278 in the perroxy-->ferryl step, and that the rate of the next step (ferryl-->oxidized) is limited by reprotonation of Glu 278 from the N-side of the membrane in the D124N mutant enzyme. The blockage of the D-pathway in this mutant for the first time allowed direct detection of deprotonation of Glu 278 and its reprotonation during oxidation of cytochrome oxidase by O2.
authors.affiliation: Structural Biology and Biophysics Program, Institute of Biotechnology, PB 65 (Viikinkaari 1), FIN-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Gorbikova
authors.forename: Nikolai P
authors.initials: NP
authors.lastname: Belevich
authors.forename: Mårten
authors.initials: M
authors.lastname: Wikström
authors.forename: Michael I
authors.initials: MI
authors.lastname: Verkhovsky
mesh_terms: D019943:Amino Acid Substitution; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism*; D010231:Paracoccus denitrificans / Q000201:enzymology* / Q000235:genetics; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003576:Electron Transport Complex IV; D010100:Oxygen