Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4

Yonghong Zhao, Ling Sun, B. K. Muralidhara, Santosh Kumar, Mark A. White, C. David Stout, James R. Halpert

Research output: Contribution to journalArticle

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Abstract

The crystal structure of P450 2B4 bound with 1-(4-chlorophenyl)imidazole (1-CPI) has been determined to delineate the structural basis for the observed differences in binding affinity and thermodynamics relative to 4-(4-chlorophenyl)imidazole (4-CPI). Compared with the previously reported 4-CPI complex, there is a shift in the 1-CPI complex of the protein backbone in helices F and I, repositioning the side chains of Phe-206, Phe-297, and Glu-301, and leading to significant reshaping of the active site. Phe-206 and Phe-297 exchange positions, with Phe-206 becoming a ligand-contact residue, while Glu-301, rather than hydrogen bonding to the ligand, flips away from the active site and interacts with His-172. As a result the active site volume expands from 200 Å 3 in the 4-CPI complex to 280 Å 3 in the 1-CPI complex. Based on the two structures, it was predicted that a Phe-206→Ala substitution would alter 1-CPI but not 4-CPI binding. Isothermal titration calorimetry experiments indicated that this substitution had no effect on the thermodynamic signature of 4-CPI binding to 2B4. In contrast, relative to wild-type 1-CPI binding to F206A showed significantly less favorable entropy but more favorable enthalpy. This result is consistent with loss of the aromatic side chain and possible ordering of water molecules, now able to interact with Glu-301 and exposed residues in the I-helix. Hence, thermodynamic measurements support the active site rearrangement observed in the crystal structure of the 1-CPI complex and illustrate the malleability of the active site with the fine-tuning of residue orientations and thermodynamic signatures.

Original languageEnglish (US)
Pages (from-to)11559-11567
Number of pages9
JournalBiochemistry
Volume46
Issue number41
DOIs
StatePublished - Oct 16 2007
Externally publishedYes

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Thermodynamics
Catalytic Domain
Substitution reactions
Crystal structure
Ligands
Calorimetry
Entropy
Hydrogen Bonding
Titration
cytochrome P-450 CYP2B4 (rabbit)
1-(4-chlorophenyl)imidazole
Enthalpy
Hydrogen bonds
Tuning
4-(4-chlorophenyl)imidazole
Molecules
Water
Proteins
Experiments

All Science Journal Classification (ASJC) codes

  • Biochemistry

Cite this

Zhao, Y., Sun, L., Muralidhara, B. K., Kumar, S., White, M. A., Stout, C. D., & Halpert, J. R. (2007). Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4. Biochemistry, 46(41), 11559-11567. https://doi.org/10.1021/bi7011614

Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4. / Zhao, Yonghong; Sun, Ling; Muralidhara, B. K.; Kumar, Santosh; White, Mark A.; Stout, C. David; Halpert, James R.

In: Biochemistry, Vol. 46, No. 41, 16.10.2007, p. 11559-11567.

Research output: Contribution to journalArticle

Zhao, Y, Sun, L, Muralidhara, BK, Kumar, S, White, MA, Stout, CD & Halpert, JR 2007, 'Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4', Biochemistry, vol. 46, no. 41, pp. 11559-11567. https://doi.org/10.1021/bi7011614
Zhao, Yonghong ; Sun, Ling ; Muralidhara, B. K. ; Kumar, Santosh ; White, Mark A. ; Stout, C. David ; Halpert, James R. / Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4. In: Biochemistry. 2007 ; Vol. 46, No. 41. pp. 11559-11567.
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AU - Stout, C. David

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