Relation of copper metabolism with the Escherchia coli respiratory chain

VOLENTINI, S. I.; FARÍAS, R. N.; RODRÍGUEZ-MONTELONGO, L.; RAPISARDA, V. A.

Mar del Plata

Congreso; XLIII Reunión Anual de SAIB; 2007

SAIB

Respiratory chain is a main focus of free radicals production in bacterial cells. Previous results of our laboratory have shown that electron flow through the Escherichia coli respiratory chain promotes the reduction of cupric ions to Cu(I), which mediates damage of the respiratory system by hydroperoxides. We have also shown that respiratory NADH dehydrogenase-2 (NDH-2) in E. coli has Cu(II)-reductase activity. In addition, NDH-2 presence decreased the susceptibility of the respiratory chain to copper and peroxides and gives the bacteria advantages to resist extreme copper concentrations. In the present work, we carried out in vivo experiments to further analyze the participation of NDH-2 and other components of the respiratory chain in the copper metabolism. We determined a specific cellular reduction of Cu(II) to Cu(I) caused only by the presence of NDH-2 and quinones, when cells were exposed to sub-lethal Cu(II) concentrations. In parallel cupric ion content, unlike cuprous ion, was increased in the NDH-2 deficient mutants. Taking together our results, NDH-2 and quinones could have a role in the copper metabolism, since Cu(II)-reduction is required by the metal uptake/export systems.