Assignment of hyperfine shifted resonances in high-spin forms of cytochrome c peroxidase by reconstitutions with deuterated hemins

Abstract

Assignments of hyperfine shifted proton resonances for the high-spin forms of cytochrome c peroxidase (EC 1.11.1.5) have been made (cytochrome c peroxidase, cytochrome c peroxidase-F) employing the technique of reconstituting the apoprotein with specifically deuterated protohemin IX derivatives. The results show that the heme methyl group pattern differs significantly from similar assignments made for metmyoglobin. In cytochrome c peroxidase the methyl pattern is 5 greater than 1 greater than 8 greater than 3. For cytochrome c peroxidase-F the pattern is 5 greater than 8 greater than 1 greater than 3, but the resonances are not shifted as far downfield and they exhibit a narrower spread. For myoglobin the relative methyl ordering has previously been shown to be 8 greater than 5 greater than 3 greater than 1. Several conclusions have been reached, including confirmation of the essential correspondence between the solution- and crystal-derived data for several heme crevice structural features. The pH dependence of the cytochrome c peroxidase-F methyl resonances is also presented and is shown to differ from native peroxidase. For cytochrome c peroxidase-F smooth, continuous titrations are observed with no evidence of the second conformation which was found for the native enzyme.