S K-edge XAS and DFT calculations on cytochrome P450: covalent and ionic contributions to the cysteine-Fe bond and their contribution to reactivity.

ABSTRACT: Experimental covalencies of the Fe-S bond for the resting low-spin and substrate-bound high-spin active site of cytochrome P450 are reported. DFT calculations on the active site indicate that one H-bonding interaction from the protein backbone is needed to reproduce the experimental values. The H-bonding to the thiolate from the backbone decreases the anisotropic pi covalency of the Fe-S bond lowering the barrier of free rotation of the exchangeable axial ligand, which is important for reactivity. The anionic axial thiolate ligand is calculated to lower the Fe(III/II) reduction potential of the active site by more than 1 V compared to a neutral imidazole ligand. About half of this derives from its covalent bonding and half from its electrostatic interaction with the oxidized Fe. This axial

SUBMITTER: Dey A 

PROVIDER: S-EPMC2734335 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature