Oxidation--reduction potentials of molybdenum and iron--sulphur centres in nitrate reductase from Escherichia coli.

The potentials of the couples Mo(IV)--(Mo(V) and Mo(V)--Mo(VI) in nitrate reductase from Escherichia coli K12 were measured as + 180 mV and + 220 mV respectively at pH 7.14. The potentials associated with two other e.p.r. signals, believed to be due to iron--sulphur centres, were measured as + 50 mV and + 80 mV.