HIGH-LEVEL INDUCIBLE EXPRESSION OF VISUAL PIGMENTS IN TRANSFECTED CELLS

A method for high-level expression of a functionally active, recombina nt human red cone opsin,cas developed by adding the coding sequence fo r the C-terminal epitope of bovine rhodopsin onto the C terminus of th e cone opsin and cloning the resulting construct into the vector pMEP4 beta. The recombinant pMEP4 beta vector was transfected stably into 2 93-EBNA cells, and expression of the cone opsin was induced by the add ition of CdCl2 into the medium. The recombinant cone opsin was reconst ituted with Il-cis retinal and purified by immunoaffinity chromatograp hy. Spectral analysis prior to and following photobleaching confirmed its identity as a red cone opsin. The protein was targeted to the cell membrane and activated bovine transducin.