(661g) Protein-Protein Binding and Structure Prediction In the Photosynthetic Antenna Complex of Green Sulfur Bacteria

A molecular understanding of protein-protein interactions in biological systems is required for effective insight into their structure and function.  For example, in photosynthetic organisms, protein-protein interactions dictate the rate and efficiency of energy transfer between chromophores.  In this work, all-atom steered molecular dynamics (SMD) simulations are carried out to calculate the free energy of protein binding to sites previously identified by docking simulations.  This enables an evaluation of the most likely configurations of the light harvesting antenna complex of green sulfur bacteria in the natural aqueous environment.  The complex consists of several pigments, such as bacteriochlorophyll A (Bchl A), and proteins, including the Fenna Matthews Olson (FMO) protein and chlorosome protein A (CsmA).  Our findings suggest, in conjunction with available experimental data, that the C-terminus of CsmA preferentially binds to FMO, facilitating the alignment of Bchl A in CsmA with Bchl A #8 in FMO. These simulations provide the necessary structures for modeling excited-state energy transfer in photosynthetic and biohybrid systems.