Antibiotic activity of thermolisin-linearized microcin analogous on Salmonella Newport

BELLOMIO, AUGUSTO; ARCURI, BEATRIZ FERNANDEZ DE; FARÍAS, RICARDO N.; MORERO, ROBERTO D.

Campinas, SP, Brasil

Congreso; IV Biophysics Congress of the Southern Cone; 2000

Sociedad Argentina de Biofísica

Microcins MccJ25 a peptide antibiotics produced by Escherichia coli is highly active on the pathogenic Salmonella species. Our previous results suggest that MccJ25 act on the cytoplasmic membrane of Salmonella newport cells, inducing gradient dissipation. MccJ25 shows to be a highly hydrophobic cyclic peptide of 21 amino acid residues. The thermolysin-linearized microcin shows a decrease in activity but was still able to inhibit the S. newport strain. In this communication we studied the antibiotic activity of seven peptides analogous of thermolysin-linearized microcin. The analogous were designed in our laboratory, synthesized by Bio-Synthesis, Inc. (USA) and purified by RP-HPLC on a semipreparative mBondapak C18, 10 mm, 300 x 19 mm column, with 20 to 100% (v/v) gradient acetonitrile/water. Antibiotic activity was determined as the minimal inhibitory concentrations by the twofold-serial dilution assay. The results indicate that the activity of MccJ25 is abolished when structural modification of the peptide hydrophilic region were provoked by replacing the amino acids His or Pro by Lys or Ala respectively. In addition the presence of a double par phenylalanine/tyrosine acquire a great importance for the peptide in order to express its activity. In conclusion the integrity of both, hydrophilic and hydrophobic, regions of the peptide are required MccJ25 antibiotic activity.