Chemical modification of microcin J25 with diethylpyrocarbonate and carbodiimide: evidence for essential histidyl and carboxyl residues

• Published in: Biochemical and biophysical research communications 2003-04, Vol.303 (2), p.458-462
• Main Authors: Bellomio, Augusto, Rintoul, Marı́a R, Morero, Roberto D
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - isolation & purification; Anti-Bacterial Agents - pharmacology; Antibiotics; Bacteriocins - chemistry; Bacteriocins - isolation & purification; Bacteriocins - pharmacology; Binding Sites; Carbodiimides; Chromatography, High Pressure Liquid; Diethyl Pyrocarbonate; Enzyme Inhibitors; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - physiology; Histidine; Microbial Sensitivity Tests; Microcin; Peptides; Plasmids; Salmonella; Salmonella - drug effects; Topoisomerase II Inhibitors
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(03)00373-5

In this paper we compared the antibacterial activity of native microcin J25, a peptide antibiotic, with the activities of two analogues obtained by chemical modifications. In the first analogue, the negative charge of glutamic carboxyl group was specifically blocked with an l-glycine methyl ester and in the second the histidine imidazole ring was carbethoxylated. Both analogues decreased notably its antibiotic activity against Escherichia coli and Salmonella newport, strains sensible to the native microcin J25. The biological activity of the carbethoxylated analogue was completely recovered after treatment with hydroxylamine. The extreme importance of both polar residues could be interpreted as specific structural features indispensable for the peptide transportation into the cell, extrusion outside the cell or alternatively to inhibit the RNA-polymerase.