Identification by ENDOR of Trp191 as the free-radical site in cytochrome c peroxidase compound ES

Mohanram Sivaraja*, David B. Goodin, Michael Smith, Brian M. Hoffman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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The chemical identity of the amino acid free-radical site that represents one of the two oxidizing equivalents stored in the H2O 2-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.

Original languageEnglish (US)
Pages (from-to)738-740
Number of pages3
Issue number4919
StatePublished - 1989

ASJC Scopus subject areas

  • General

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