Redox-active tyrosine residue in the microcin J25 molecule.

MIRIAM CHALÓN; NATALIA WILKE; JENS PEDERSEN; STEFANO RUFINI; ROBERTO D. MORERO; LEONARDO CORTEZ; ROSANA CHEHIN; FARÍAS, RICARDO N.; PAULA VINCENT

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2011 vol. 406 p. 366 - 370

0006-291X

Microcin J25 (MccJ25) is a 21 amino acid lasso-peptide antibiotic produced by Escherichia coli and composedof an 8-residues ring and a terminal ‘tail’ passing through the ring. We have previously reportedtwo cellular targets for this antibiotic, bacterial RNA polymerase and the membrane respiratory chain,and shown that Tyr9 is essential for the effect on the membrane respiratory chain which leads to superoxideoverproduction. In the present paper we investigated the redox behavior of MccJ25 and the mutantMccJ25 (Y9F). Cyclic voltammetry measurements showed irreversible oxidation of both Tyr9 and Tyr20 inMccJ25, but infrared spectroscopy studies demonstrated that only Tyr9 could be deprotonated uponchemical oxidation in solution. Formation of a long-lived tyrosyl radical in the native MccJ25 oxidizedby H2O2 was demonstrated by Electron Paramagnetic Resonance Spectroscopy; this radical was notdetected when the reaction was carried out with the MccJ25 (Y9F) mutant. These results show thatthe essential Tyr9, but not Tyr20, can be easily oxidized and form a tyrosyl radical.