PERSONAL DE APOYO
GIRO Mariana
congresos y reuniones científicas
Título:
Contribution of zwf and fpr genes to oxidative stress tolerance in Escherichia coli
Autor/es:
GIRÓ MARIANA; CARRILLO NÉSTOR; KRAPP ADRIANA
Lugar:
Pinamar, Buenos Aires
Reunión:
Congreso; XLI Reunión Anual Nacional de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB), PABMB y SAN; 2005
Institución organizadora:
Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular
Resumen:
Glucose 6-phosphate dehydrogenase (G6PDH) and ferredoxin-NADP(H) reductase (FPR), encoded by the zwf and fpr genes, respectively, are committed members of the SoxRS regulatory system involved in superoxide resistance in Escherichia coli. Exposure of E. coli cells to superoxide led to rapid accumulation of G6PDH, while FPR induction was delayed. Bacteria over-expressing G6PDH displayed a protracted soxRS response, whereas FPR build-up had the opposite effect. Inactivation of any of the two genes resulted in enhanced sensitivity to MV killing relative to the wild-type strain. Accumulation of G6PDH over wild-type levels had no effect on MV tolerance, while FPR over-expression led to augmented survival. Recovery of damaged iron-sulphur clusters of hydro-lyases after oxidative challenge was faster and more extensive in transformed bacteria expressing FPR than in wild-type cells, indicating that the reductase contributed to this repair pathway in vivo. Reactivation could also be accomplished in a defined system containing both enzymes, their substrates and  FPR acceptors ferredoxin or flavodoxin. G6PDH and FPR could act concertedly during the soxRS response to deliver reducing equivalents from carbohydrates, via NADP+, to critical repair pathways of the stressed cell. Glucose 6-phosphate dehydrogenase (G6PDH) and ferredoxin-NADP(H) reductase (FPR), encoded by the zwf and fpr genes, respectively, are committed members of the SoxRS regulatory system involved in superoxide resistance in Escherichia coli. Exposure of E. coli cells to superoxide led to rapid accumulation of G6PDH, while FPR induction was delayed. Bacteria over-expressing G6PDH displayed a protracted soxRS response, whereas FPR build-up had the opposite effect. Inactivation of any of the two genes resulted in enhanced sensitivity to MV killing relative to the wild-type strain. Accumulation of G6PDH over wild-type levels had no effect on MV tolerance, while FPR over-expression led to augmented survival. Recovery of damaged iron-sulphur clusters of hydro-lyases after oxidative challenge was faster and more extensive in transformed bacteria expressing FPR than in wild-type cells, indicating that the reductase contributed to this repair pathway in vivo. Reactivation could also be accomplished in a defined system containing both enzymes, their substrates and  FPR acceptors ferredoxin or flavodoxin. G6PDH and FPR could act concertedly during the soxRS response to deliver reducing equivalents from carbohydrates, via NADP+, to critical repair pathways of the stressed cell.