ULTRA-HIGH RESOLUTION STRUCTURE OF NATIVE AND ENZYME INTERMEDIATE OF CYTOCHROME

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cytochrome c peroxidase (CcP) from yeast is a soluble heme-containing protein found in the mitochondrial electron transport chain where it probably protects against toxic peroxides. It catalyzes the oxidation of two molecules of ferrocytochrome c to ferricytochrome c concomitant with the reduction of hydrogen peroxide to water. During the course of the reaction cycle with hydrogen peroxide it forms a semi-stable intermediate termed Compound I, which has a half-life of about 6 h. The Compound I contains a semi-stable radical centered on Trp191 and an oxyferryl (Fe4+=O) heme group. The aim of this study is to obtain a reliable structure of the native CcP and its enzyme intermediate Compound I to near atomic resolution so as to study the structural details of the reaction with substrates and to determine the nature of Trp191 radical which cannot be determined by conventional methods.