FTIR studies of internal proton transfer reactions linked to inter-heme electron transfer in bovine cytochrome c oxidase |
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| Authors: | McMahon Benjamin H Fabian Marian Tomson Farol Causgrove Timothy P Bailey James A Rein Francisca N Dyer R Brian Palmer Graham Gennis Robert B Woodruff William H |
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| Institution: | Chemistry Division, Bioscience Division, and Center for Nonlinear Studies, Los Alamos National Laboratory, Michelson Res., Bioscience Division, Los Alamos, NM 87545, USA. |
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| Abstract: | FTIR difference spectroscopy is used to reveal changes in the internal structure and amino acid protonation states of bovine cytochrome c oxidase (CcO) that occur upon photolysis of the CO adduct of the two-electron reduced (mixed valence, MV) and four-electron reduced (fully reduced, FR) forms of the enzyme. FTIR difference spectra were obtained in D(2)O (pH 6-9.3) between the MV-CO adduct (heme a(3) and Cu(B) reduced; heme a and Cu(A) oxidized) and a photostationary state in which the MV-CO enzyme is photodissociated under constant illumination. In the photostationary state, part of the enzyme population has heme a(3) oxidized and heme a reduced. In MV-CO, the frequency of the stretch mode of CO bound to ferrous heme a(3) decreases from 1965.3 cm(-1) at pH*
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