Microcin J25 inhibits cytochrome bd oxido reductase activity

GALVÁN E; CHALÓN MC; ACUÑA L; SCHURIG-BRICCIO L; MINAHK CJ; GENNIS R; BELLOMIO A

Rosario

Congreso; SAIB L Reunión Anual; 2014

SAIB

Microcin J25 (MccJ25) is a plasmid-encoded antimicrobial lasso peptide produced by Escherichia coli. It displaysantibiotic activity against a range of Gram-negative pathogens including E. coli, Salmonella and Shigella. MccJ25has two cellular targets, the RNA polymerase and the membrane respiratory chain. MccJ25 targets the respiratorychain enzymes on the bacterial membrane with the consequent inhibition of oxygen consumption. This effect ismediated by an increase in superoxide production during the membrane respiratory processes. E. coli has twoterminal oxidoreductases, the cytochrome bd and cytochrome bo3 in their respiratory system. The E. coli C43 strain(wild type) was sensitive to the peptide whereas the ΔbdI ΔbdII double mutant became fully resistant. In ourlaboratory, cytochrome bdI was purified and the effect of MccJ25 on the activity of this terminal oxidase was studied.The ubiquinol oxidase activity was significantly inhibited in presence of MccJ25. This inhibition was dose dependent.Furthermore, the analysis of the kinetic constants Km and Vmax allowed us to conclude that MccJ25 would act as anon-competitive inhibitor. This finding indicates that this lasso peptide would be capable of inhibiting the ubiquinolactivity in vitro suggesting that the cytochrome bd might constitute a main target in E. coli membrane chain.