WILKE NATALIA
Congresos y reuniones científicas
Título:
A MccJ25 tyrosil radical is involved in the respiratory chain inhibition by the antimicrobial peptide
Autor/es:
M.C. CHALON, N. WILKE, M.V. NIKLISON CHIROU, L. CORTEZ, A. BELLOMIO, R.D. MORERO, R. CHEHÍN, R.N. FARÍAS Y P.A. VINCENT.
Reunión:
Congreso; XXXVIII Reunión anual de la Sociedad Argentina de Biofísica; 2011
Resumen:
MccJ25 is an antimicrobial peptide that targets both, the transcription process and the bacterial
membrane respiratory chain, inhibiting cell oxygen consumption. This last effect is mediated by
an increase in superoxide production by the respiratory processes. Tyr9 of MccJ25 was
demonstrated as essential for the action on the respiratory chain. Redox-active tyrosine
residues play important roles in catalysis in several enzymes, including ribonucleotide
reductase, prostaglandin H synthase, and Photosystem II [1]. Here we investigated the tyrosil
radical formation in MccJ25 using Electronic Paramagnetic Resonance (EPR) and Fourier
transform infrared spectroscopy (2D-FTIR). The tyrosil radical was detected by EPR when
MccJ25 was incubated in the presence of H2O2 and DBNBS (trapping of the tyrosil radical).
Moreover, FTIR experiments showed an increment of tyrosil radical band located at 1,478 cm-1
in the spectrum. Moreover the redox potential of microcina J25 was determinated by cyclic
voltammetry techniques and an irreversible oxidation at about 970 mV vs calomel electrode was
detected, a value corresponding to tyrosine oxidation. On other hand, MccJ25 was unable to
inhibited respiratory chain enzymes activities when the experiments were performed with
membranes obtained from E. coli deficient in cytochrome bd and quinones production
pathways. These results confirm the presence of a tyrosil radical in MccJ25 molecule and
suggest that it could be formed by oxidation in the respiratory chain. Moreover, we proposed
that cytochrome bd and quinores are essential for the MccJ25 effect on respiratory chain.
[1] Vassiliev, I. R., Offenbacher, A. R., Barry, B. A.,J. Phys. Chem. B., 2005,109:23077-23085.
membrane respiratory chain, inhibiting cell oxygen consumption. This last effect is mediated by
an increase in superoxide production by the respiratory processes. Tyr9 of MccJ25 was
demonstrated as essential for the action on the respiratory chain. Redox-active tyrosine
residues play important roles in catalysis in several enzymes, including ribonucleotide
reductase, prostaglandin H synthase, and Photosystem II [1]. Here we investigated the tyrosil
radical formation in MccJ25 using Electronic Paramagnetic Resonance (EPR) and Fourier
transform infrared spectroscopy (2D-FTIR). The tyrosil radical was detected by EPR when
MccJ25 was incubated in the presence of H2O2 and DBNBS (trapping of the tyrosil radical).
Moreover, FTIR experiments showed an increment of tyrosil radical band located at 1,478 cm-1
in the spectrum. Moreover the redox potential of microcina J25 was determinated by cyclic
voltammetry techniques and an irreversible oxidation at about 970 mV vs calomel electrode was
detected, a value corresponding to tyrosine oxidation. On other hand, MccJ25 was unable to
inhibited respiratory chain enzymes activities when the experiments were performed with
membranes obtained from E. coli deficient in cytochrome bd and quinones production
pathways. These results confirm the presence of a tyrosil radical in MccJ25 molecule and
suggest that it could be formed by oxidation in the respiratory chain. Moreover, we proposed
that cytochrome bd and quinores are essential for the MccJ25 effect on respiratory chain.
[1] Vassiliev, I. R., Offenbacher, A. R., Barry, B. A.,J. Phys. Chem. B., 2005,109:23077-23085.
