The electron coupled proton transfer (ECPT) event is fundamental for many energy conversion processes in biological systems including the mitochondrial cytochrome bc1 complex. The bc1 complex operates by a prototypical Q-cycle and catalyzes electron transfer in ubiquinol (QH2) oxidation (Qo site) and ubiquinone (Q) reduction (Qi site), coupled to the translocation of protons, generating a proton gradient that drives ATP synthesis. Understanding the details underlying the ECPT process in bc1 will advance our knowledge of how nature regulates energy conversion efficiently and thus advance our strategies toward achieving renewable energy sources. We used molecular dynamic simulations to examine the binding geometries of Q at the Qi site. Our results showed that the Qi pocket consists of mostly non-polar residues, in excellent agreement with X-ray crystallographic structures, yet water molecules still have free access to the Qi site. The role of water bridged hydrogen bonds in substrate binding will be discussed.

Role of water bridged hydrogen bonds in ubiquinone binding geometries at the Qi site of cytochrome bc1

245th National Meeting (2013)

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