This family includes fluorescence recovery protein (FRP) domain, which is found in Synechocystis sp. PCC 6803 substr. Kazusa. FRP causes the dissociation of the orange carotenoid protein (OCP) from the phycobilisomes by interacting with the C-terminal domain of OCP, accelerating the conversion of the active red OCP to the inactive orange form. A patch of residues (W50, D54, H53, and R60), contributed by both chains of the FRP dimer cause the acceleration of the OCPr to OCPo conversion. Mutation of the absolutely conserved amino acids (R60) affect the activity of FRP [1].

1: Crystal structure of the FRP and identification of the active site for modulation of OCP-mediated photoprotection in cyanobacteria. Sutter M, Wilson A, Leverenz RL, Lopez-Igual R, Thurotte A, Salmeen AE, Kirilovsky D, Kerfeld CA; Proc Natl Acad Sci U S A. 2013;110:10022-10027. PMID:23716688