Anti-bovine rhodopsin monoclonal antibody recognizing light-dependent structural change

The antigenic structure of the bovine rhodopsin molecule was investigated by using a bovine rhodopsin-specific monoclonal antibody designated Rh29. Competition assay with sealed intact disks and broken disks indicated that the antibody-binding region was localized in the intradiscal surface. An anti-genic peptide obtained by a cyanogene bromide cleavage of rhodopsin was purified and determined as residues 2-39 in the amino acid sequence. Further analysis suggested that the antigenic determinant included at least residues 21-25. These results were consistent with the structural model for membrane topology of rhodopsin. The antigenicity of the rhodopsin was compared among several states. The antibody bound to both ammonyx LO-solubilized unbleached and bleached rhodopsin. In contrast, upon membrane-embedded rhodopsin, unbleached one was 100-times less antigenic than bleached one. The results suggested that the segment around the determinant of membrane-embedded rhodopsin should undergo a structural change upon absorption of light. Rh29 detected a band corresponding to bovine, porcine and octopus opsins in immunoblotting. Protein blot of crayfish rhabdome did not show any reactive band. These bands except for crayfish reacted with concanavalin A as well. The N-terminal structure may, therefore, conserved between mammal and erthropoda and diverge between them and cepharopoda.