Protein phosphatase 2A removes the phosphates from phosphorylated rhodopsin (p MII) and phosphorylated opsin (p-RHO) (Fowles et al. 1989, Palczewski et al. 1989a,b). A Ca2+ dependent opsin phosphatase is also present (Kutuzov & Bennett 1996). Serine/threonine protein phosphatases with EF hands (PPEF1 and 2) that share homology with Drosophila retinal degeneration C (rdgC) are expressed in retina and may be responsible (Huang & Honkanen 1998), there is no evidence for a physiological role in dephosphorylating rhodopsin. Once dephosphorylated, RHO can once again bind the chromophore 11 cis retinal (11cRAL), in readiness for the next photon response. Arrestin (S-antigen or SAG, Yamaki et al. 1988) binds to and sterically caps MII, preventing PPEF1 from dephosphorylating it.