The antibiotic peptide Microcin J25 is a redox peptide

CHALÓN M.; CORTEZ L.; CHEHÍN R.; FARÍAS R.; VINCENT P

Carlos Paz- Córdoba

Congreso; Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular.; 2008

SAIB

Two cellular targets for the antibiotic peptide Microcin J25 (MccJ25), the RNA polymerase and membrane respiratory chain via the superoxide production, was previously reported by our group. Tyr 9 is the key amino acid in the membrane target of the antibiotic. FTIR spectroscopy was used in order to detect the peptide´s Tyr reduction. The wavenumber shifting from 1,514.6 to 1,512.2 cm-1 in the presence of potassium ferrocyanide, could be related with the Tyr-OH specie due to the reduction. The effect of MccJ25 on the the tetrazolium salt MTT reduction, mediated by phenazine methosulfate (PMS) was analyzed by spectroscopy techniques. Changes in the IR spectrum of the Tyr radical band located at 1,478 cm-1, was detected by using 2D-FTIR. In the same way, MccJ25 was capable to inhibit in a concentration dependent way, the electronic flow from NADH to MTT through PMS, probably due to a competitive effect exerted by the peptide. In absence of MTT, lower oxygen consumption was obtained by the addition of MccJ25. On the contrary, in the presence of MTT, no oxygen consumption was observed without MccJ25, suggesting that the electrons flow straight to MTT. Therefore, when MccJ25 was added, the oxygen consumption was observed due to the fact that microcin is able to transfer electrons to oxygen molecule. These data led us to propose Mirocin J25 as a redox antibiotic peptide.