期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1807, 期 1, 页码 80-84出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2010.08.014
关键词
Proton pump; Heme-copper oxidase; MD simulation; Proton-coupled electron transfer; Continuum electrostatics
资金
- Biocentrum Helsinki
- Academy of Finland
- Sigrid Juselius Foundation
- Viikki Graduate School in Molecular Biosciences
Cellular respiration is driven by cytochrome c oxidase (CcO), which reduces oxygen to water and couples the released energy to proton pumping across the mitochondrial or bacterial membrane. Proton pumping in CcO involves proton transfer from the negatively charged side of the membrane to a transient proton-loading or pump site (PLS), before it is ejected to the opposite side. Although many details of the reaction mechanism are known, the exact location of the PLS has remained elusive. We report here results from combined classical molecular dynamics simulations and continuum electrostatic calculations, which show that the hydrogen-bonded system around the A-propionate of heme a(3) dissociates reversibly upon reduction of heme a. The dissociation increases the pK(a) value of the propionate to a value above similar to 9, making it accessible for redox-state dependent protonation. The redox state of heme a is of key importance in controlling proton leaks by polarizing the PLS both statically and dynamically. These findings suggest that the propionate region of heme a(3) fulfills the criteria of the pump site in the proton translocation mechanism of CcO. (C) 2010 Elsevier B.V. All rights reserved.
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