Table 1.

Localization of ferric reductase in M. magnetotacticuma

FractionActivity
Ferric reductase (nmol min−1)Nitrite reductase (μmol min−1)Malate dehydrogenase (μmol min−1)
Periplasm00.431.9
Cytoplasm8.3016.1
Membrane2.4NDb ND
  • a After cells in 10 mM Tris-HCl buffer (pH 8.0) containing 0.75 M sucrose were incubated with EDTA plus lysozyme at 30°C for 1 h, the membrane, periplasmic fraction, and cytoplasmic fractions were prepared as described in Materials and Methods.N,N,N′,N′-tetramethyl-p-phenylenediamine [Ph(NMe2)2]-nitrite reductase activity was followed by measuring the increase inA 606. The reaction mixture contained 10 mM sodium phosphate (pH 6.5), 1 mM Ph(NMe2)2, 0.1 mM sodium nitrite, and the protein sample in a total volume of 1.0 ml. Malate dehydrogenase activity was followed by measuring the decrease inA 340. The reaction mixture for the malate dehydrogenase assay contained 100 mM potassium phosphate (pH 7.5), 0.25 mM NADH, 0.2 mM oxaloacetic acid, and protein sample.

  • b ND, not determined.