Abstract The photoactive Orange Carotenoid Protein (OCP) plays a key role in
cyanobacterial photoprotection. In OCP, a single non-covalently bound keto-carotenoid
molecule acts as a light intensity sensor, while the protein is responsible for forming
molecular contacts with the light-harvesting antenna, the fluorescence of which is quenched
by OCP. Activation of this physiological interaction requires signal transduction from the
photoexcited carotenoid to the protein matrix. Recent works revealed an asynchrony …