Persistence of species variation and regional heterogeneity of the apparent molecular masses of benzodiazepine‐binding proteins after deglycosylation

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Abstract
Brain membrane preparations of different vertebrates were photoaffinity labeled with [3H]flunitrazepam and subsequently deglycosylated with endoglycosidase F and peptide N‐glycopeptidase. SDS‐polyacrylamide gel electrophoresis followed by fluorography revealed that each benzodiazepine‐binding protein is deglycosylated in two steps, indicating that each protein has two glycosylation sites. Species variation of the apparent molecular masses of the benzodiazepine‐binding proteins and regional heterogeneity in avians persist after deglycosylation. These results indicate that the α‐subunit(s) of the GABA/benzodiazepine receptor has undergone electrophoretically detectable changes in its amino acid composition during vertebrate evolution. The existence of at least two different α‐subunits in avians is further substantiated.