Báo cáo Y học: The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus A comparative study on the redox properties of the metal clusters present in the dinitrogenase components

The dinitrogenase component proteins of the conventional Mo nitrogenase (MoFe protein) and of the alternative Fe-only nitrogenase (FeFe protein) were both isolated and purified from Rhodobacter capsulatus, redox-titrated according to the same procedures and subjected to an EPR spectroscopic comparison. In the course of an oxidative titration of the MoFe protein (Rc1Mo) three significant S ¼ 1/2 EPR signals deriving from oxidized states of the P-cluster were detected: (1) a rhombic signal (g ¼ 2.07, 1.96 and 1.83), which showed a bell-shaped redox curve with midpoint potentials (Em) of )195 mV (appearance) and )30 mV (disappearance), (2) an axial signal...