Evidence on intramolecular electron transfer in the MoFe protein of nitrogenase from Klebsiella pneumoniae from rapid-freeze electron-paramagnetic-resonance studies of its oxidation by ferricyanide

A transient e.p.r. signal with g-values of 2.05, 1.95 and 1.81 was observed in rapid-freezing experiments when Kpl, the MoFe protein of nitrogenase from Klebsiella pneumoniae, was oxidized by ferricyanide or by some dyes. This e.p.r. signal was assigned to the 'P'-centres and, since such signals are characteristics of [4Fe-4S]1+ clusters, provides further evidence for the 'P'-centres being in the [4Fe-4S]0 oxidation level in the …