Mutagenesis of a single hydrogen bond in cytochrome P-450 alters cation binding and heme solvation.

Abstract Cytochrome P-450cam, a monoxygenase responsible for the regiospecific hydroxylation of camphor, binds its substrate through complimentary van der Waals contacts and the formation of a single hydrogen bond between tyrosine 96 and the ketone group of camphor. Substrate association is positively regulated through the binding of a monovalent cation and the oxidation-reduction potential modulated by the spin state of the ferric heme controlled by water access to the sixth coordination site of the iron. Removal of this single hydrogen bond via site-directed mutagenesis of tyrosine 96 to phenylalanine 96 defines this aspect of the protein structure as responsible for the linkage between cation and substrate cooperativities, the degree of spin state conversion resulting from water access via macromolecule and substrate dynamics, and suggests a specific location for the cation binding site.