Electron and proton transfer to the quinones in bacterial photosynthetic reaction centers: insight from combined approaches of molecular genetics and biophysics.

We present here new results together with an overview of the current knowledge on the coupled processes of electron and proton transfer in bacterial reaction centers. The importance of a multidisciplinary approach associating molecular genetics, structural biology, biochemistry and spectroscopy is underlined. We emphasize the electrostatic role of the protein to maintain a negative electrostatic potential near the second quinone electron acceptor in order to: i) accelerate the overall rate of proton transfer from the cytoplasm to this acceptor by increasing the pKs of some groups involved in this process; ii) increase the local proton concentration near this acceptor. We also point out the possibility of long distance propagation of the electrostatic effects through the protein associated with relaxation processes triggered by the formation of the semiquinone anions on the first flash.