We tested 18 antisera showing reactivity against the α subunit of transducin, the guanine nucleotide binding protein from rod outer segment, for crossreactivity against the 40- and 39-kDa guanine nucleotide binding proteins purified from bovine brain. A single antiserum, CW6, showed crossreactivity, and this was predominantly against the 40-kDa protein. Immunoblots of the tryptic fragments of transducin α subunit with multiple antisera raised against that subunit showed that only CW6 recognizes a COOH-terminal 5-kDa peptide that includes the site of pertussis toxin ADP-ribosylation. Antibodies against the 5-kDa peptide, affinity-purified from CW6, specifically react with the 40-kDa brain protein on immunoblots. The results show that the 39- and 40-kDa guanine nucleotide binding proteins from brain differ immunochemically and that the COOH-terminal 5-kDa peptide of transducin α subunit is homologous to a region in the 40-kDa brain protein. We speculate that this homologous region may be in a domain that confers specificity for receptor interactions of guanine nucleotide binding proteins.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 1985|
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