The Heme-Based Oxygen Sensor Rhizobium etli FixL: Influence of Auxiliary Ligands on Heme Redox Potential and Implications on the Enzyme Activity

Midpoint potentials assigned to the FeIII/II redox couple of the heme domain of FixL from Rhizobium etli (ReFixL) were determined for the unliganded state (+ 19 mV) and bounded to CO (+ 21 mV), O2 (− 51 mV), imidazole (− 57 mV) and CN− (− 156 mV) and support a correlation with the kinase activity.108