3qu8

Publication Abstract from PubMed

The biochemical, biophysical, and structural analysis of the cytochrome P450 2B subfamily of enzymes has provided a wealth of information regarding conformational plasticity and substrate recognition. The recent x-ray crystal structure of the drug metabolizing P450 2B6 in complex with 4-(4-chlorophenyl)imidazole (4-CPI) yielded the first atomic view of this human enzyme. However, knowledge of the structural basis of P450 2B6 specificity and inhibition has remained limited. In this study, structures of P450 2B6 were determined in complex with the potent inhibitors 4-benzylpyridine (4-BP) and 4-(4-nitrobenzyl)pyridine (4-NBP). Comparison of the present structures with the previous P450 2B6-4-CPI complex showed that reorientation of side chains of active site residue Phe206 on the F-helix and Phe297 on the I- helix was necessary to accommodate the inhibitors. However, P450 2B6 does not require any major side chain rearrangement to bind 4-NBP compared with 4-BP, nor does the enzyme provide hydrogen-bonding partners for the polar nitro group of 4-NBP within the hydrophobic active site. Additionally, based on these new structures, substitution of residue 172 with histidine as observed in the single nucleotide polymorphism Q172H and in P450 2B4 may contribute to a hydrogen bonding network connecting the E- and I-helices, thereby stabilizing active site residues on the I-helix. These results provide insight into the role of active site side chains upon inhibitor binding and indicate that the recognition of the benzylpyridines in the closed conformation structure of P450 2B6 is based solely on hydrophobicity, size, and shape.

Structures of Cytochrome P450 2B6 Bound to 4-Benzylpyridine and 4-(4-Nitrobenzyl)pyridine: Insight into Inhibitor Binding and Rearrangement of Active Site Side Chains.,Shah MB, Pascual J, Zhang Q, Stout CD, Halpert JR Mol Pharmacol. 2011 Aug 29. PMID:21875942^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.