Aborycin – A Tricyclic 21‐Peptide Antibiotic Isolated from Streptomyces griseoflavus

The screening for growth inhibitors against Bacillus subtilis revealed a peptide antibiotic produced by Streptomyces griseoflavus TÜ 4072. Very high yields of the antibiotic named aborycin were obtained by cultivation in a medium containing soybean meal and sucrose. Isolation from the mycelium was carried out by a combination of extraction and gel chromatography. Preparative HPLC yielded the uniform antibiotic. The structure elucidation was based on GC amino acid analysis on a chiral phase, automated Edman degradation, electrospray tandem mass spectrometry and two‐dimensional NMR (TOCSY, ROESY, HSQC, HMBC). Aborycin represents a 21‐peptide that is cyclized from the side chain of Asp 9 to the N‐terminus of Cys 1 . Two disulfide bonds Cys 1 to Cys 13 and Cys 7 to Cys 19 form a tricyclic structure consisting exclusively of protein amino acids. The peptide antibiotic aborycin was found to be identical with a HIV protease inhibitor isolated recently from Streptomyces SP 9440. magnified image