High levels of rhodopsin phosphorylation in missense mutations of C-terminal region of rhodopsin.

Rhodopsin phosphorylation was investigated using synthetic C-terminal peptides from rhodopsin. The peptides were phosphorylated by expressed rhodopsin kinase (RK) in the presence of a photolyzed truncated rhodopsin at the C-terminus. No peptide phosphorylation was detected under dark or in conditions in which RK was inactive. However, the phosphorylation rate was significantly higher in the following three peptides: (345M Rho, 330DDEASTTVSKTETSQMAPA; 347S Rho, 330DDEASTTVSKTETSQVASA; and 347L Rho: 330DDEASTTVSKTETSQVALA) taken from missense mutations of rhodopsin found in patients with autosomal retinitis pigmentosa (ADRP) as compared with that from wild-type rhodopsin (330DDEASTTVSKTETSQVAPA). Distribution of the phosphorylation showed a similar ratio among three serines (334, 338 and 343) in 347L Rho mutation to wild type. However, 345M Rho and 347S Rho peptides showed higher phosphorylation at Ser334. The data obtained suggests that an abnormally high rate of phosphorylation in missense mutations around the rhodopsin C-terminus may change the position of phosphorylation and inactivation process of the visual transduction.