INVESTIGADORES
VOLENTINI Sabrina Ines
congresos y reuniones científicas
Título:
CELLULAR CU(II)-REDUCTION BY E. COLI RESPIRATORY CHAIN IN COPPER EXPORTERS DEFICIENT STRAINS
Autor/es:
VOLENTINI, SABRINA I.; SCHURIG BRICCIO LA; RINTOUL MR; FARIAS, R. N.; RODRIGUEZ MONTELOGO L; RAPISARDA, V. A.
Lugar:
Carlos Paz - Argentina
Reunión:
Congreso; XLIV Reunión Anual de SAIB ( Sociedad Argetnina de Bioquimica y Biologia Molecular); 2008
Institución organizadora:
SAIB
Resumen:
Copper is both an
essential nutrient and a toxic element able to catalyze free radical formation.
In E. coli there are two copper exporters: a P-type ATPase CopA and a
multi-component transport system CusCFBA. All proteins of the copper
homeostatisis use Cu(I), although the copper reductase activity is still
unclear. Previous results of our laboratory have shown that electron flow
through the E. coli respiratory chain promotes the reduction of cupric
ions by NADH dehydrogenase-2 and quinones. Here we measured Cu(II)-reduction as
the rate of Cu(I) appearance in supernatant of cellular suspensions exposed to
sub-lethal Cu(II) concentrations using strains lacking several respiratory
chain components and/or copper exporters. Without CopA or Cus system, the
Cu(II)-reduction rate decreased around 50% respect to the wild-type strain. In
the absence of NDH-2, this decrease was nearly 10%, but interestingly a double
mutant lacking CopA and NDH-2 recovered the reduction level of the wild-type.
In the absence of quinones, the Cu(II)-reduction rate decreased 60-80%. To
understand the mentioned events, membranes NADH and
D-Lactate:Cu(II)-oxidoreductase activities of different mutants were assayed.
We proposed two copper reduction mechanisms in E. coli: one of them
occurs in cytoplasm and is mediated by both NDH-2 and quinones and the other to
the periplasmic side and is mediated only by quinones.