Fluorescence recovery protein: a powerful yet underexplored regulator of photoprotection in cyanobacteria
Cyanobacteria utilize an elegant photoprotection mechanism mediated by the photoactive Orange Carotenoid Protein (OCP), which upon binding dissipates excess energy from light-harvesting complexes – phycobilisomes. OCP activity is efficiently regulated by its partner – the Fluorescence Recovery Protein (FRP). FRP accelerates OCP conversion to the resting state thus counteracting OCP-mediated photoprotection. Behind the deceptive simplicity of such regulation hides a multistep process involving dramatic conformational rearrangements in OCP and FRP, the details of which become clearer only a decade after FRP discovery. Yet many questions regarding functioning of FRP remain controversial. In this review, we summarize current knowledge and understanding of the FRP role in cyanobacterial photoprotection as well as its evolutionary history that presumably lies far beyond cyanobacteria.