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Energy diagrams and mechanism for proton pumping in cytochrome c oxidase
- Source :
-
BBA - Bioenergetics . Sep2007, Vol. 1767 Issue 9, p1143-1156. 14p. - Publication Year :
- 2007
-
Abstract
- Abstract: The powerful technique of energy diagrams has been used to analyze the mechanism for proton pumping in cytochrome c oxidase. Energy levels and barriers are derived starting out from recent kinetic experiments for the O to E transition, and are then refined using general criteria and a few additional experimental facts. Both allowed and non-allowed pathways are obtained in this way. A useful requirement is that the forward and backward rate should approach each other for the full membrane gradient. A key finding is that an electron on heme a (or the binuclear center) must have a significant lowering effect on the barrier for proton uptake, in order to prevent backflow from the pump-site to the N-side. While there is no structural gating in the present mechanism, there is thus an electronic gating provided by the electron on heme a. A quantitative analysis of the energy levels in the diagrams, leads to Prop-A of heme a3 as the most likely position for the pump-site, and the Glu278 region as the place for the transition state for proton uptake. Variations of key redox potentials and pK a values during the pumping process are derived for comparison to experiments. [Copyright &y& Elsevier]
- Subjects :
- *HEMOGLOBINS
*BLOOD pigments
*BLOOD proteins
*CYTOCHROMES
Subjects
Details
- Language :
- English
- ISSN :
- 00052728
- Volume :
- 1767
- Issue :
- 9
- Database :
- Academic Search Index
- Journal :
- BBA - Bioenergetics
- Publication Type :
- Academic Journal
- Accession number :
- 26413886
- Full Text :
- https://doi.org/10.1016/j.bbabio.2007.06.009