RGS9-1 is phosphorylated in darkness at Ser475 by protein kinase C (PRKC, specifically the isozymes PRKCalpha and PRKCtheta). Phosphorylation significantly decreases the affinity of RGS9 for RGS9-1 anchor protein (R9S9BP) thus representing a potential mechanism for feedback control of the kinetics of photoresponse recovery in both rods and cones (Sokal et al. 2003, Balasubramanian et al. 2001, Hu et al. 2001). Dephosphorylation is mediated by protein phosphatase 2A.