Active-site analysis of ferric P450 enzymes: hydrogen-bonding effects on the circular dichroism spectra

Active-site CD spectra were analyzed for P450's with known x-ray structures (P450terp, P450BM-3, P450cam). CD spectral patterns for Fe(3+)-substrate-free P450's reflect structure/function properties of the distal pocket. P450terp and P450BM-3 have an H-bond between 6th ligand and I-helix [Hasemann, C.A., et al. (1995) Structure, 3, 41-62], and the Soret CD band at approximately 410 nm is approximately 2-fold larger than that at approximately 350 nm. For P450cam, the two CD bands are more nearly equal, and the 6th ligand is not H-bonded to the I-helix. The CD spectral pattern can be used to predict active-site structural properties, e.g., H-bonding and polarity.