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  • Title: Palmitoylation of bovine opsin and its cysteine mutants in COS cells.
    Author: Karnik SS, Ridge KD, Bhattacharya S, Khorana HG.
    Journal: Proc Natl Acad Sci U S A; 1993 Jan 01; 90(1):40-4. PubMed ID: 8419942.
    Abstract:
    Previously, bovine rhodopsin has been shown to be palmitoylated at cysteine residues 322 and 323. Here we report on palmitoylation of bovine opsin in COS-1 cells following expression of the synthetic wild-type opsin gene and several of its cysteine mutants in the presence of [3H]palmitic acid. Two moles of palmitic acid are introduced per wild-type opsin molecule in thioester linkages. Palmitoylation is abolished when both Cys-322 and Cys-323 are replaced by serine residues. Replacement of Cys-322 by serine prevents palmitoylation at Cys-323, whereas replacement of the latter with serine allows palmitoylation at Cys-322. Opsin mutants that evidently do not contain a Cys-110/Cys-187 disulfide bond and presumably remain in the endoplasmic reticulum are not palmitoylated. Replacement of Cys-140 or Cys-185 reduces the extent of palmitoylation of the opsin. Lack of palmitoylation at Cys-322 and/or Cys-323 does not affect 11-cis-retinal binding, absorption maximum or extinction coefficient of the chromophore, the bleaching behavior of the chromophore, or the light-dependent binding and activation of transducin. Mutants containing serine substitutions at Cys-140 or Cys-323 showed reduced light-dependent phosphorylation by rhodopsin kinase.
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