The effects of an engineered cation site on the structure, activity, and EPR properties of cytochrome c peroxidase

Destabilization of the Trp191 cationic radical impairs the activity and electron paramagnetic resonance signal in cytochrome c peroxidase. This was gleaned from an experiment in which the cytochrome c peroxidase mutant crystal structure has been refined to 1.5 Angstroms using data derived at cryogenic temperatures. The inherent electron paramagnetic resonance signal associated with the Trp19 radical is progressively reduced as K(super +) is added. The increase in (K(super +)) also results in the loss in enzyme activity.