title: Binding sites of photoreceptor-specific antibodies COS-1, OS-2 and AO.
abstract: The chicken red-sensitive cone visual pigment (iodopsin) and several synthetic peptides of cone and rod visual pigments were used to find the binding sites of our photoreceptor-specific antibodies with immunocytochemistry. The ability of iodopsin to block immunolabeling with monoclonal antibodies COS-1 and OS-2 furnished direct evidence that both antibodies are specific to visual pigments. Immunocytochemistry on whole-mount retinas with and without detergent, as well as electron microscopic labeling of cone photoreceptor membranes revealed the binding sites of COS-1 and OS-2 to be on the cytoplasmic side of the membrane. By testing several synthetic peptides, mainly from the C-terminal region of the cone visual pigments, we found that the domain consisting of the last 6 amino acids of the human red/green-, and the chicken red-sensitive cone pigments completely blocked immunolabeling with COS-1, while the sequence consisting of the last 12 amino acids of the human blue cone pigment was effective to block the binding of OS-2. Both monoclonals can be regarded therefore C-terminal specific antibodies. OS-2 was found to bind to the dark-adapted photopigment more strongly than to the light-adapted one. The binding of the polyclonal rhodopsin antibody AO was almost entirely inhibited by the N-terminal synthetic peptide of bovine rhodopsin indicating that this antibody binds primarily to the N-terminal domain of rhodopsin in a tissue environment.
authors.affiliation: Laboratory I of Electron Microscopy, Semmelweis University of Medicine, Budapest, Hungary.
authors.forename: P
authors.initials: P
authors.lastname: Röhlich
authors.forename: A
authors.initials: A
authors.lastname: Szél
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000918:Antibody Specificity; D001665:Binding Sites; D002645:Chickens; D003623:Dark Adaptation; D006168:Guinea Pigs; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D008027:Light; D008297:Male; D051379:Mice; D008875:Middle Aged; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D010786:Photoreceptor Cells / Q000276:immunology / Q000378:metabolism*; D012168:Retinal Pigments / Q000378:metabolism*; D013552:Swine
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D009842:Oligopeptides; D012168:Retinal Pigments