Quinone Dynamics Within the Photosynthetic Reaction Center of Rhodobacter Sphaeroides Investigated by Molecular Dynamics Simulations
Joshua Vermaas, University of Illinois at Urbana-Champaign
Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis in Rhodobacter sphaeroides, a model organism for photosynthesis. Prior experimental results have shown that the photosynthetic reaction center in Rhodobacter sphaeroides is only fully functional with a limited set of quinones, suggesting that ubiquinone-specific interactions are required to drive electron transport and the formation of a quinol. The identity of this interaction has not been uniquely determined experimentally. Through parameterization and computational modeling of ubiquinone and two monomethoxy ubiquinone derivatives, we have developed a complete picture of the prominent interactions present between quinones in the Qa and Qb sites. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Qb site and the amide nitrogen of GlyL225 that we implicate in tuning the redox potential difference between the quinones in the Qa and Qb sites. The disruption of this interaction leads to weaker binding of species which lack a 2-methoxy group, calculated in this study via thermodynamic integration.
Abstract Author(s): Josh V. Vermaas, Alexander T. Taguchi, Colin A. Wraight, Emad Tajkhorshid