Sequence and Expression of the Murine Diazepam Binding Inhibitor

Previous studies suggest that a diazepam binding inhibitor (DBI, also referred to as endozepine) present in the brain may function anxiogenically as a modulator of the gamma-aminobutyric acid receptor complex (GABAA). An expression library representing mouse brain mRNA was screened using antisera that recognizes the 11 kDa DBI protein. A cDNA clone was isolated and sequenced. Comparison of the amino acid sequence of mouse DBI to that for human, rat and bovine DBI shows that the size of DBI is conserved at 87 amino acids in all of these mammals. DBI cDNA hybridizes to an mRNA of about 600 nucleotides. This mRNA is not restricted to the brain, being prevalent in other organs such as the liver and kidney. Its moderate to high abundance, as judged from mRNA levels, in several organs suggests that DBI might have functions other than, or in addition to, the possible regulation of benzodiazepine binding sites.