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.
Bennett, N, Kutuzov, MA
McDowell, JH, Ingebritsen, TS, Hargrave, PA, Jakes, S, Palczewski, K
Honkanen, RE, Huang, X
Xiong, WH, Yau, KW, Ramulu, P, Nathans, J, Blesh, D, Williams, J, Kennedy, M, Hurley, JB, Cowan, M
Shinohara, T, Tsuda, M, Yamaki, K
McDowell, JH, Ingebritsen, TS, Hargrave, PA, Palczewski, K
Fowles, C, Cohen, P, Akhtar, M
protein serine/threonine phosphatase activity of PPEF1:Mg2+ [cytosol]
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