Cytochrome c oxidase (CcO), the terminal enzyme in the electron transport chain, couples proton pumping to the reduction of dioxygen into water. The coupling mechanism remains to be elucidated. Previous studies have identified several mutations within CcO's primary proton uptake pathway (the D-channel) that decouple proton pumping from redox activity. Here, I examine the molecular basis for decoupling in single and double mutants of highly conserved residues, D132 and N139, in order to gain insight into the coupling mechanism. In particular, I use molecular dynamics and free energy simulations of a new, unconstrained model of bacterial CcO embedded in a solvated lipid bilayer to investigate how such mutants affect functional hydration and ionic selectivity in the D-channel. Results support earlier mechanistic insights obtained in our laboratory from simplified molecular models and predict a new, testable hypothesis by which cations such as K+ may inhibit proton pumping in charged mutants of N139.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/33352 |
| Date | 21 November 2012 |
| Creators | Caplan, David |
| Contributors | Pomès, Régis |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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