Proton motive force dissipation enhances the reactive oxygen species overproduction of microcin J25.

DUPUY, FERNANDO; NIKLISON CHIROU, MARIA VICTORIA; FERNANDEZ DE ARCURI, BEATRIZ; CHEHÍN, ROSANA; BELLOMIO, AUGUSTO; MINAHK, CARLOS; MORERO, ROBERTO

La Plata, Buenos Aires

Congreso; XXXVII Reunión Anual de la Sociedad Argentina de Biofísica; 2008

Sociedad Argentina de Biofísica

Microcin J25 is a 21 aminoacid peptide active against Escherichia coli and Salmonella enteritidis strains. The structure of MccJ25 was elucidated based on mass spectrometry and nuclear magnetic resonance showing a distinctive lasso-structure with high hydrophobic character. The first target described in E. coli was the bf subunit of the RNA polymerase. However, it was also shown that MccJ25 inhibited the respiratory enzymes of plasma membrane in S. enteritidis serovar Newport and induced the overproduction of reactive oxygen species, suggesting that the antibacterial activity involved more than one primary target. Previous work from our laboratory has also provided evidence of membrane binding of MccJ25 in model membrane systems. In order to study the interaction of the antibiotic with bacterial membranes, a purified fluorescein labeled peptide was incubated with membranes vesicles or with membranes obtained by sonication and ultracentrifugated. Both Gram negative and Gram positive bacteria were used as membrane sources for assessing the specificty of peptide-membrane interaction. The protonophore agent 2,4-dinitrophenol did not affect peptide-membrane binding, although diminished the intracellular accumulation of the antibiotic and prevented RNA polymerase inhibition. However, almost no changes in antimicrobial activity could be seen. As increased reactive oxygen species overproduction was observed when bacteria were treated with 2,4 dinitrophenol and MccJ25, we suggest that these deleterious species could account for the bactericidal mechanism of action of MccJ25 and enhance the activity of other antibiotics.