Spectroscopic Characterization ofaNewlyIsolated Cytochrome P450 fromRhodococcus rhodochrous

Cytochrome P450(P450) fromRhodococcus rhodochrous havebeencharacterized through circular dichroism andnuclear magnetic resonance(NMR)spectroscopy, bothinthesubstrate-free andsubstrate-bound forms. Thedataare compared withthoseofP450cam andindicate a closesimilarity ofthestructure oftheactive siteinthetwoproteins. The substrate-free species contains low-spin iron(lIl), while the2-ethoxyphenol boundspecies contains high-spin iron(lIl). The substrate isinslowexchange ontheNMR timescale. Thebinding ofCN-hasbeeninvestigated andthefinal adductchar- acterized through NMR spectra. Nuclear relaxation times oftheisotropically shifted signals turn outtobeshorter thaninother hemeproteins, bothinthehigh- andinthelow-spin species. Thisistheresult oflonger electron relaxation times inP450sthaninperoxidases andmetmyoglobin. This property, aswell astheelectron paramagnetic resonance(EPR) spectrum ofthesubstrate-free form, arediscussed interms ofthepresenceofthecysteine asthefifth ligand oftheiron ioninstead ofahistidine asitoccursinperoxidases andmyoglobin.