Oxidative Phosphorylation in Fractionated Bacterial Systems

The involvement of metal in oxidation and coupled phosphorylation by cell-free preparations of Mycobacterium phlei was examined. The oxidation of succinate was inhibited by metal-chelating agents, but with β-hydroxybutyrate, chelating agents exhibited an uncoupling effect. The site of inhibition was found to be between the flavoprotein and the cytochrome b regions of the electron transport chain. The inhibitory action of o-phenanthroline was reversed by ferrous ions but not by other divalent metal ions. Ferrous ions restored both oxidation and phosphorylation with succinate and could effectively counteract the uncoupling action of o-phenanthroline on the oxidation of β-hydroxybutyrate. These results suggest that nonheme iron may be involved in the electron transport pathway of M. phlei.