Molecular Cloning, Primary Structure, and Orientation of the Vertebrate Photoreceptor Cell Protein Peripherin in the Rod Outer Segment Disk Membrane

Peripherin, a 39-kDa membrane protein, has been previously localized to the rim region of the vertebrate rod photoreceptor disk membrane by use of monoclonal antibodies and immunocytochemical labeling techniques. As an initial step in determining the structure and function of this protein, we have cloned and sequenced cDNA containing its complete coding sequence. A bovine retinal λgtl 1 expression library was screened with the antibodies, and a 583 base pair clone was initially isolated. The remaining part of the coding sequence was obtained from subsequent rescreenings of the same library and an independent λgtlO library. A C-terminal CNBr fragment of peripherin was purified by immunoaffinity chromatography and reverse-phase high-performance liquid chromatography. The amino acid sequence of the isolated C-terminal peptide and the N-terminal sequence analysis of immunoaffinity-purified peripherin are in agreement with the cDNA sequence. The cDNA sequence predicts that there are possibly four transmembrane domains. On the basis of immunocytochemical studies and sequence analysis, the hydrophilic C-terminal segment containing the antigenic sites for the antiperipherin monoclonal antibodies has been localized on the cytoplasmic side of the disk membrane. There are three consensus sequences for aspar-agine-linked glycosylation. Deglycosylation studies have indicated that at least one of these sites is utilized. The possible function of peripherin in relation to its primary structure is discussed.