MICROCIN J25 INHIBITS CYTOCHROME BD OXIDOREDUCTASE ACTIVITY

GALVÁN, EMILCE; CHALÓN MIRIAM; ACUÑA, LEONARDO; SCHURIG BRICCIO LICI; MINAHK, CARLOS JAVIER; GENNIS ROBERT; BELLOMIO, AUGUSTO

Rosario

Congreso; Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

Microcin J25 (MccJ25) is a plasmid-encoded antimicrobial lasso peptide produced by Escherichia coli. It displays antibiotic activity against a range of Gram-negative pathogens including E. coli, Salmonella and Shigella. MccJ25 has two cellular targets, the RNA polymerase and the membrane respiratory chain. MccJ25 targets the respiratory chain enzymes on the bacterial membrane with the consequent inhibition of oxygen consumption. This effect is mediated by an increase in superoxide production during the membrane respiratory processes. E. coli has two terminal 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 ∆bdI ∆bdII double mutant became fully resistant. In our laboratory, 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 a non-competitive inhibitor. This finding indicates that this lasso peptide would be capable of inhibiting the ubiquinol activity in vitro suggesting that the cytochrome bd might constitute a main target in E. coli membrane chain.