title: Identification by ENDOR of Trp191 as the free-radical site in cytochrome c peroxidase compound ES.
abstract: The chemical identity of the amino acid free-radical site that represents one of the two oxidizing equivalents stored in the H2O2-oxidized intermediate (compound ES) of the mitochondrial heme enzyme, cytochrome c peroxidase (CcP) has been sought for almost a quarter of a century. Site-directed mutagenesis alone cannot yield this answer. Low-temperature 35-gigahertz (Q-band) electron nuclear double resonance (ENDOR) spectroscopy was used to examine compound ES prepared from proteins containing specifically deuterated methionine or tryptophan, as well as the amino acid replacement Trp51----Phe. The results definitely identify the site of the radical in compound ES as tryptophan, most likely Trp191.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208.
authors.forename: M
authors.initials: M
authors.lastname: Sivaraja
authors.forename: D B
authors.initials: DB
authors.lastname: Goodin
authors.forename: M
authors.initials: M
authors.lastname: Smith
authors.forename: B M
authors.initials: BM
authors.lastname: Hoffman
mesh_terms: D001665:Binding Sites; D003578:Cytochrome-c Peroxidase / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology; D005609:Free Radicals; D009154:Mutation; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000235:genetics; D011994:Recombinant Proteins; D014364:Tryptophan
chemical_list: D005609:Free Radicals; D011994:Recombinant Proteins; D014364:Tryptophan; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase