Production of antibodies against rhodopsin after immunization with beta gamma-subunits of transducin: evidence for interaction of beta gamma-subunits of guanosine 5'-triphosphate binding proteins with receptor.
The light-detecting system of retinal rod outer segments is regulated by a guanyl nucleotide binding (G) protein, transducin, which is composed of alpha-, beta-, and gamma-subunits. Transducin couples rhodopsin to the intracellular effector enzyme, a cGMP phosphodiesterase. The beta gamma complex (T beta gamma) is required for the alpha-subunit (T alpha) to interact effectively with the photon receptor rhodopsin. It is not clear, however, whether T beta gamma binds directly to rhodopsin or promotes T alpha binding to rhodopsin only by binding to T alpha. We have found that serum from rabbits immunized with T beta gamma contained a population of antibodies that were reactive against rhodopsin. These antibodies could be separated from T beta gamma antibodies by absorbing the latter on immobilized transducin. Binding of purified rhodopsin antibodies was inhibited by T beta gamma, suggesting that the rhodopsin antibodies and T beta gamma bound to the same site on rhodopsin. We propose that the rhodopsin antibodies act both as antiidiotypic antibodies against the idiotypic T beta gamma antibodies and as antibodies against rhodopsin. This hypothesis is consistent with the conclusion that T beta gamma interacts directly with the receptor. It is probable that in an analogous way, G beta gamma interacts directly with receptors of the adenylate cyclase system.
D000818:Animals; D000906:Antibodies / Q000302:isolation & purification*; D000936:Antigen-Antibody Complex; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay; D019204:GTP-Binding Proteins / Q000276:immunology* / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D010786:Photoreceptor Cells / Q000378:metabolism*; D012168:Retinal Pigments / Q000276:immunology*; D012243:Rhodopsin / Q000276:immunology* / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000378:metabolism; D015293:Transducin
D000906:Antibodies; D000936:Antigen-Antibody Complex; D046911:Macromolecular Substances; D008565:Membrane Proteins; D012168:Retinal Pigments; D012243:Rhodopsin; D019204:GTP-Binding Proteins; D015293:Transducin