VINCENT Paula Andrea
congresos y reuniones científicas
Escherichia coli cell-free extracts contain an antibiotic activity with the specificity of MccJ25
CECILIA VALLEJOS; PAULA VINCENT; RAÚL SALOMÓN
Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular; 2006
Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular
The 21-residue peptide antibiotic microcin J25 (MccJ25) surges from a precursor of 58 amino acids. Our long term goal is the elucidation of the mechanistic details of MccJ25 maturation. As a first step toward an in vitro maturation system, we are trying to purify the precursor protein. For that purpose, cell-free extracts of E. coli cells harbouring a plasmid encoding the MccJ25 precursor were subjected to HPLC analysis. One of the peaks showed antibiotic activity against Salmonella Newport (an indicator strain hypersusceptible to MccJ25) and some strain of E. coli. A likely explanation is that the precursor itself has antibiotic activity. Surprisingly, however, extracts from plasmidless E. coli K-12 cells also showed the same activity, and this substance was inactive against MccJ25-resistant mutants or strains harbouring the MccJ25 immunity gene. Preliminary experiments showed this compound to be a peptide. It is tempting to speculate that the E. coli chromosome encodes a product structurally similar to MccJ25 or, at least, with the same specificity of action. Purification of this substance is under way, but is hampered by the fact that it is present in very little amounts in cell extracts.