2bdm

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spinqualitylabelsall models 2bdm, resolution 2.300Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of Cytochrome P450 2B4 with Bound Bifonazole

Overview

To better understand ligand-induced structural transitions in cytochrome, P450 2B4, protein-ligand interactions were investigated using a bulky, inhibitor. Bifonazole, a broad spectrum antifungal agent, inhibits, monooxygenase activity and induces a type II binding spectrum in, 2B4dH(H226Y), a modified enzyme previously crystallized in the presence of, 4-(4-chlorophenyl)imidazole (CPI). Isothermal titration calorimetry and, tryptophan fluorescence quenching indicate no significant burial of, protein apolar surface nor altered accessibility of Trp-121 upon, bifonazole binding, in contrast to recent results with CPI. A 2.3 A, crystal structure of 2B4-bifonazole reveals a novel open conformation with, ligand bound in the active site, which is significantly different from, either the U-shaped cleft of ligand-free 2B4 or the small active site, pocket of 2B4-CPI. The O-shaped active site cleft of 2B4-bifonazole is, widely open in the middle but narrow at the top. A bifonazole molecule, occupies the bottom of the active site cleft, where helix I is bent, approximately 15 degrees to accommodate the bulky ligand. The structure, also defines unanticipated interactions between helix C residues and, bifonazole, suggesting an important role of helix C in azole recognition, by mammalian P450s. Comparison of the ligand-free 2B4 structure, the, 2B4-CPI structure, and the 2B4-bifonazole structure identifies, structurally plastic regions that undergo correlated conformational, changes in response to ligand binding. The most plastic regions are, putative membrane-binding motifs involved in substrate access or substrate, binding. The results allow us to model the membrane-associated state of, P450 and provide insight into how lipophilic substrates access the buried, active site.

About this Structure

2BDM is a Single protein structure of sequence from Oryctolagus cuniculus with HEM, TMI and CM5 as ligands. Active as Unspecific monooxygenase, with EC number 1.14.14.1 Full crystallographic information is available from OCA.

Reference

Structure of microsomal cytochrome P450 2B4 complexed with the antifungal drug bifonazole: insight into P450 conformational plasticity and membrane interaction., Zhao Y, White MA, Muralidhara BK, Sun L, Halpert JR, Stout CD, J Biol Chem. 2006 Mar 3;281(9):5973-81. Epub 2005 Dec 21. PMID:16373351

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