Microcin J25 induces ATP depletion in Escherichia coli cells

MIRIAM CHALÓN; AUGUSTO BELLOMÍO; RICARDO FARÍAS; RAÚL SALOMÓN; PAULA A. VINCENT

Rosario, Argentina

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

After entering sensitive cells through the outer membrane receptor FhuA, the 21-residue peptide antibiotic microcin J25 (MccJ25) displays a dual mechanism of action: it inhibits both RNA polymerase (RNAP) and cell respiration. The latter effect is apparently mediated by an overproduction of superoxide radical which, in turn, would affect superoxide-sensitive enzymes from the respiratory chain, leading to a reduction in the intracellular levels of ATP. In the present work, we examined the effect of MccJ25 on E. coli ATP levels using a luciferin-luciferase bioluminescence method. Our results show that MccJ25 induces a significant ATP reduction in the MccJ25-hypersensitive strain AB1133, whereas no effect was detected by using strain MC4100, which has an intrinsic partial resistance to the antibiotic. A drop in ATP levels took place also in PA232 (pGC01), a strain that carries a mutated MccJ25-resistant RNAP and overexpress the FhuA receptor (encoded by plasmid pGC01). Previously, we observed that the increase in superoxide radical production caused by MccJ25 was prevented by the addition of the enzyme superoxide dismutase (SOD). Since only a small ATP depletion occurred when cells were coincubated with MccJ25 and SOD, we conclude that the fall in ATP levels is a consequence of superoxide production induced by MccJ25, and that this effect is independent of RNAP inhibition.