Antibodies against a retinal guanine nucleotide‐binding protein cross‐react with a single plasma membrane protein in non‐retinal tissues

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Abstract
Antisera (AS/1‐AS/6) to purified bovine retinal transducin, a guanine nucleotide‐binding protein, were produced in 6 rabbits. Immunoblots showed that the antisera varied in their reactivity with the subunits of transducin; AS/1 reacted strongly with all 3 subunits, while the others reacted with only the β and/or γ subunits. Only AS/1 specifically immunoprecipitated the α subunit radiolabeled with non‐covalently bound guanine nucleotides. Immunostaining of plasma membrane proteins from non‐retinal tissues with AS‐1 revealed a single protein (approx. 35 kDa), most likely representing the β subunit of the guanine nucleotide‐binding proteins (Gs and gi associated with adenylate cyclase. Cerebral cortex showed the highest content of this protein. Antisera against transducin provide a highly specific and sensitive probe for quantitation of the β subunit of Gs and Gi