title: Estriol bound and ligand-free structures of sterol 14alpha-demethylase.
abstract: Sterol 14alpha-demethylases (CYP51) are essential enzymes in sterol biosynthesis in eukaryotes and drug targets in antifungal therapy. Here, we report CYP51 structures in ligand-free and estriol bound forms. Using estriol as a probe, we determined orientation of the substrate in the active site, elucidated protein contacts with the invariant 3beta-hydroxy group of a sterol, and identified F78 as a key discriminator between 4alpha-methylated and 4alpha,beta-dimethylated substrates. Analysis of CYP51 dynamics revealed that the C helix undergoes helix-coil transition upon binding and dissociation of a ligand. Loss of helical structure of the C helix in the ligand-free form results in an unprecedented opening of the substrate binding site. Upon binding of estriol, the BC loop loses contacts with molecular surface and tends to adopt a closed conformation. A mechanism for azole resistance in the yeast pathogen Candida albicans associated with mutations in the ERG11 gene encoding CYP51 is suggested based on CYP51 protein dynamics.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. larissa.m.podust@vanderbilt.edu
authors.forename: Larissa M
authors.initials: LM
authors.lastname: Podust
authors.forename: Liudmila V
authors.initials: LV
authors.lastname: Yermalitskaya
authors.forename: Galina I
authors.initials: GI
authors.lastname: Lepesheva
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Podust
authors.forename: Enrique A
authors.initials: EA
authors.lastname: Dalmasso
authors.forename: Michael R
authors.initials: MR
authors.lastname: Waterman
mesh_terms: D000595:Amino Acid Sequence; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism; D004964:Estriol / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D015335:Molecular Probes; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D058886:Sterol 14-Demethylase; D013379:Substrate Specificity
chemical_list: D008024:Ligands; D015335:Molecular Probes; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D004964:Estriol