text: The OCP participates in key protein–protein interactions that are critical to its photoprotective function.  The activated OCP form binds to allophycocyanin in the core of the phycobilisome and initiates the OCP-dependent photoprotective quenching mechanism.  Another protein, the fluorescence recovery protein (FRP), interacts with the CTD in OCP and catalyzes the reaction which reverts it back to the OCP form.  Because OCP cannot bind to the phycobilisome antenna, FRP effectively can detach OCP from the antenna and restore full light-harvesting capacity.