Interaction of the orange carotenoid protein with the phycobilisome core and fluorescence recovery protein

Using methods of molecular modeling, we have derived a universal spatial model of the orange carotenoid protein (OCP) and phycobilisome (PBS) core interaction in process of energy excess dissipation. The protrusion of the phy-cobilin domain (PB) of the core-membrane linker polypeptide (L_cm) forms the interaction site for the OCP central cavity on the PBS core surface. This spatial arrangement has to be the most advantageous one because the L_CM, as the major terminal PBS-fluorescence emitter, gathers energy from the other phycobiliproteins within the PBS before quenching by OCP. In agreement with the constructed model, the small fluorescence recovery protein (FRP) also interacts with the OCPs central cavity weakening the PBS and OCP binding.