The antibiotic peptide Microcin J25 is a redox peptide

CHALON MIRIAM; CORTEZ LEONARDO; CHEÍN ROSANA; FARÍAS RICARDO; VINCENT PAULA

Carlos Paz, Córdoba, Argentina

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

The microcin J25 (MccJ25) is a lasso-peptide antibiotic of 21 L-amino acid residues (G1-G-A-G-H5-V-P-E-Y-F10-V-G-I-G-T15-P-I-S-F-Y20-G). Two cellular targets for the antibiotic, the RNA polymerase and membrane respiratory chain via the superoxide production, were previously reported by our group. Also, we showed that Tyr9 is the key amino acid in the membrane respiratory chain target of the antibiotic. Now, we studied the electronic flow from NADH to MTT through phenazine methosulfate (PMS) by spectroscopy techniques, 2D-FTIR and oxygen consumption, in the presence of MccJ25. MccJ25 was capable to inhibit the tetrazolium salt (MTT) reduction in a concentration dependent way. We observed, in the reaction, an increment of both i) Tyr radical band located at 1,478 cm-1 in the IR spectrum and ii) the oxygen consumption. In the absence of MccJ25 the electrons flow directly to MTT since no oxygen consumption was observed. The last fact suggested that microcin is able to transfer electrons to oxygen molecule. FTIR spectroscopy was also used in order to detect the peptide´s Tyr reduction in the presence of potassium ferro/ferricyanide. The wavenumber related with the Tyr-OH specie shifted from 1,514.6 to 1,512.2 cm-1. These data led us to propose MccJ25 as a redox antibiotic peptide.