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

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Abstract
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 adsorbing 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. 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.

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