Research: Project 4
The mechanisms of the electron transfer-coupled proton pumps.
To make ATP, the chloroplast couples exergonic electron transfer reactions to translocation of protons across the thylakoid membrane. The resulting pmf is used to drive the endergonic synthesis of ATP. We have focused on the reactions of the cytochrome b6f complex and related cytochrome bc1 complexes (of bacteria and mitochondria). These enzymes oxidize hydroquinones (quinols) and reduce soluble electron carriers. The energy released in this process is used to pump protons, probably via a mechanism called a Q-cycle, which is responsible for producing about one-third of all of the ATP in plants. Under adverse conditions, the cytochrome b6f/bc1 complexes can also produce, as a byproduct,superoxide, which in turn can lead to diseases, including some associated with aging in humans. To understand (and potentially control) these processes, we are investigating the molecular structure and mechanism of these complexes using a range of biophysical and molecular techniques.