THE CYCLIC STRUCTURE OF THE ENTEROCOCCAL PEPTIDE ANTIBIOTIC AS-48

The complete primary structure of the peptide antibiotic AS-48 produce d by Enterococcus faecalis has been determined by chemical degradation analysis. The cyclic nature of this 70 residues containing peptide wa s demonstrated by plasma desorption mass analysis of the generated pep tides and electrospray ionisation mass analysis of the native polypept ide. As far as we know, this is the first example of an antibiotic pro tein cyclised by a tail-head peptide bond formation and not by branchi ng of the polypeptide side chains.