THE CRYSTAL-STRUCTURE OF THE IRON-FREE CYTOCHROME-C PEROXIDASE AND ITS IMPLICATION FOR THE ENZYMATIC MECHANISM

We report the refined structure of an iron-free form of cytochrome c p eroxidase (CcP) at 2.3 Angstrom,resolution. The backbone comparison be tween native CcP and iron-free CcP shows that the two structures have the same protein fold within experimental error. The only difference n oted is in the heme pocket where the distance between the proximal. hi stidine and the center of the protoporphyrin has increased. The result s show that the iron-free CcP should be a good substitute for native C cP in fluorescence studies and thus also validate previous studies usi ng iron-free CcPs as efficient fluorescent probes in electron transfer studies.