Structure of mammalian cytochrome P450 2B4 complexed with 4-(4-chlorophenyl)imidazole at 1.9-Å resolution

Insight into the range of P450 conformations and the coordination of redox partner binding

Emily E. Scott, Mark White, You Ai He, Eric F. Johnson, C. David Stout, James R. Halpert

Research output: Contribution to journalArticle

276 Citations (Scopus)

Abstract

A 1.9-Å molecular structure of the microsomal cytochrome P450 2B4 with the specific inhibitor 4-(4-chlorophenyl)imidazole (CPI) in the active site was determined by x-ray crystallography. In contrast to the previous experimentally determined 2B4 structure, this complex adopted a closed conformation similar to that observed for the mammalian 2C enzymes. The differences between the open and closed structures of 2B4 were primarily limited to the lid domain of helices F through G, helices B′ and C, the N terminus of helix I, and the β4 region. These large-scale conformational changes were generally due to the relocation of conserved structural elements toward each other with remarkably little remodeling at the secondary structure level. For example, the F′ and G′ helices were maintained with a sharp turn between them but are placed to form the exterior ceiling of the active site in the CPI complex. CPI was closely surrounded by residues from substrate recognition sites 1, 4, 5, and 6 to form a small, isolated hydrophobic cavity. The switch from open to closed conformation dramatically relocated helix C to a more proximal position. As a result, heme binding interactions were altered, and the putative NADPH-cytochrome P450 reductase binding site was reformed. This suggests a structural mechanism whereby ligand-induced conformational changes may coordinate catalytic activity. Comparison of the 2B4/CPI complex with the open 2B4 structure yields insights into the dynamics involved in substrate access, tight inhibitor binding, and coordination of substrate and redox partner binding.

Original languageEnglish (US)
Pages (from-to)27294-27301
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number26
DOIs
StatePublished - Jun 25 2004

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Oxidation-Reduction
Conformations
Catalytic Domain
Substrates
NADPH-Ferrihemoprotein Reductase
Crystallography
Relocation
Ceilings
Molecular Structure
Heme
Molecular structure
Catalyst activity
Binding Sites
Switches
X-Rays
Ligands
X rays
Enzymes
imidazole
4-(4-chlorophenyl)imidazole

ASJC Scopus subject areas

  • Biochemistry

Cite this

Structure of mammalian cytochrome P450 2B4 complexed with 4-(4-chlorophenyl)imidazole at 1.9-Å resolution : Insight into the range of P450 conformations and the coordination of redox partner binding. / Scott, Emily E.; White, Mark; He, You Ai; Johnson, Eric F.; Stout, C. David; Halpert, James R.

In: Journal of Biological Chemistry, Vol. 279, No. 26, 25.06.2004, p. 27294-27301.

Research output: Contribution to journalArticle

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abstract = "A 1.9-{\AA} molecular structure of the microsomal cytochrome P450 2B4 with the specific inhibitor 4-(4-chlorophenyl)imidazole (CPI) in the active site was determined by x-ray crystallography. In contrast to the previous experimentally determined 2B4 structure, this complex adopted a closed conformation similar to that observed for the mammalian 2C enzymes. The differences between the open and closed structures of 2B4 were primarily limited to the lid domain of helices F through G, helices B′ and C, the N terminus of helix I, and the β4 region. These large-scale conformational changes were generally due to the relocation of conserved structural elements toward each other with remarkably little remodeling at the secondary structure level. For example, the F′ and G′ helices were maintained with a sharp turn between them but are placed to form the exterior ceiling of the active site in the CPI complex. CPI was closely surrounded by residues from substrate recognition sites 1, 4, 5, and 6 to form a small, isolated hydrophobic cavity. The switch from open to closed conformation dramatically relocated helix C to a more proximal position. As a result, heme binding interactions were altered, and the putative NADPH-cytochrome P450 reductase binding site was reformed. This suggests a structural mechanism whereby ligand-induced conformational changes may coordinate catalytic activity. Comparison of the 2B4/CPI complex with the open 2B4 structure yields insights into the dynamics involved in substrate access, tight inhibitor binding, and coordination of substrate and redox partner binding.",
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