Complete amino acid sequences of bovine and human endozepines. Homology with rat diazepam binding inhibitor

Abstract

The complete amino acid sequences of bovine and human brain endozepines have been determined. The amino-terminal serine of both endozepines is acylated. Assignment of the first 7 residues was achieved through Edman degradation after acid-induced rearrangement and subsequent acid hydrolysis of the amino-terminal blocking group. Cleavage of endozepine by chemical and enzymatic techniques established all the fragments in an unambiguous sequence. Bovine and human endozepines are single-chain polypeptides of 86 residues, with calculated molecular weights of 9913, displaying 93% homology. A comparison between the sequences of bovine and human endozepines with the partial sequences of the functionally related diazepam binding inhibitor from rat brain reveals significant sequence homology. The reported results suggest that bovine and human endozepines as well as rat diazepam binding inhibitor belong to a new family of polypeptides which presumably take part in the modulation of gamma-aminobutyric acid-ergic transmission.