Potential Energy Landscape for Conformationally Gated Secondary Ubiquinone Binding in the Photosynthetic Reaction Center of Rhodobacter Sphaeroides

Abstract

Migration of the secondary ubiquinone, UQB, to a site proximal to His-L190 was proposed to be rate-determining for electron transfer in bacterial photosynthetic reaction centers (shown). This study shows that 1) the proximal binding site is the global minimum on the potential energy landscape, 2) multiple minima exist, in qualitative agreement with various binding sites observed in X-ray diffraction studies, and 3) the energy barrier for direct migration of UQB and migration gated by a protein conformational change both agree with the activation energy measured for electron transfer.