Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors.

Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors. Research Abstract Details 

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Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors. Abstract Text:

B K Muralidhara,Ling Sun,Surendra Negi,James R Halpert,

Structural plasticity of mammalian cytochromes P450 (CYP) has recently been explored in our laboratory and elsewhere to understand the ligand-binding promiscuity. CYP2B4 exhibits very different conformations and thermodynamic signatures in binding the small inhibitor 4-(4-chlorophenyl)imidazole (4-CPI) versus the large bifonazole. Using four key active-site mutants (F296A, T302A, I363A, and V367L) that are involved in binding one or both inhibitors, we dissected the thermodynamic basis for the ability of CYP2B4 to bind substrates and inhibitors of different sizes and chemistry. In all cases, 1:1 binding stoichiometry was observed. The inhibitors 4-CPI, 1-(4-chlorophenyl)imidazole, and 1-(2-(benzyloxy)ethyl)imidazole bind to the mutants with a free energy difference (DeltaDeltaG) of approximately 0.5 to 1 kcal/mol compared with the wild type but with a large entropy-enthalpy compensation of up to 50 kcal/mol. The substrate testosterone binds to all four mutants with a DeltaDeltaG of approximately 0.5 kcal/mol but with as much as 40 kcal/mol of entropy-enthalpy compensation. In contrast, benzphetamine binding to V367L and F296A is accompanied by a DeltaDeltaG of approximately 1.5 and 3 kcal/mol, respectively. F296A, I363A, and V367L exhibit very different benzphetamine metabolite profiles, indicating the different substrate-binding orientations in the active site of each mutant. Overall, the findings indicate that malleability of the active site allows mammalian P450s to exhibit a high degree of thermodynamic fidelity in ligand binding.

Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors. Publishing Authors By Initials

BK Muralidhara,L Sun,S Negi,JR Halpert,

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Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors. Journal Published:

PUBLICATION TYPE: Journal Article

Journal: Journal of molecular biology

VOLUME: 377

Page Numbers: 232-45

Journal Abbreviation: J. Mol. Biol.

ISSN: 1089-8638

DAY: 5

MONTH: 01

YEAR: 2008

Thermodynamic Fidelity of the Mammalian Cytochrome P450 2B4 Active Site in Binding Substrates and Inhibitors. Information

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LANGUAGE: eng

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AFFILIATION: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA.

Country: England

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MEDLINETA: J Mol Biol

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