BIOINORGANIC CHEMISTRY A Short Course Second Edition

370 IRON-CONTAINING PROTEINS AND ENZYMES

heme (cation radical +•) cannot be unequivocally determined from the X - ray
crystallographic structures.
Structural details for the ferric P450 – camphor complex (PDB: 1DZ4) were
found to be very similar to those found for the PDB: 2CPP structure obtained
by Poulos et al.^36 In the PDB: 1DZ4 X - ray structure, the heme iron ion is
covalently attached to the thiolate sulfur of cys357. The heme is ruffl ed and
the fi ve - coordinate iron is out of the porphyrin plane by 0.3 Å. The camphor
substrate resides in the distal heme pocket held by a single hydrogen bond
between its carbonyl oxygen and the side - chain hydroxyl of tyr96. A carboxyl-
ate group on the D pyrrole ring of the porphyrin (see Figure 7.1 ) forms a

Figure 7.17 Visualization of cytochrome P450 ’ s active site with camphor — the acti-
vated oxygen intermediate (PDB: 1DZ9). Visualized using CambridgeSoft Chem3D
Ultra 10.0 with notations in ChemDraw Ultra 10.0. (Printed with permission of
CambridgeSoft Corporation.)

C 5

H 2 O 903

H 2 O 687

H 2 O 566

H 2 O 523

tyr96

thr101

asp251

thr252

cys357 glu36 6

camphor

2.8

2.8 3.0

1.67

2.3

2.6 2.5 4.1

3.4

2.8

3.0

PDB: 1DZ9 active site

All distances in angstroms