title: Molecular basis for the interaction of four different classes of substrates and inhibitors with human aromatase.
abstract: Aromatase cytochrome P450 (CYP19) converts androgen to estrogen. In this study, the interactions of four classes of compounds, 17beta-estradiol (the product of aromatase), 17-methyltestosterone (a synthetic androgen), dibenzylfluorescein (a synthetic substrate of aromatase), and coumestrol (a phytoestrogen), with aromatase were investigated through spectral analysis using purified human recombinant aromatase and site-directed mutagenesis studies using CHO cells expressing wild-type human aromatase or five aromatase mutants, E302D, D309A, T310S, S478T and H480Q. Spectral analysis showed that a type I binding spectrum was produced by the binding of 17-methyltestosterone to aromatase and a novel binding spectrum of aromatase was induced by dibenzylfluorescein. Mutagenesis experiments demonstrated that residues S478 and H480 in the beta-4 sheet play an important role in the binding of all four compounds. Computer-assisted docking of these compounds into the three-dimensional model of aromatase revealed that: (1) weak interaction between 17beta-estradiol and the beta-4 sheet of aromatase facilitates the release of 17beta-estradiol from the active site of aromatase; (2) 17-methyl group of 17-methyltestosterone affects its binding to aromatase; (3) dibenzylfluorescein binds to the active site of aromatase with its O-dealkylation site near the heme iron and residue T310; and (4) coumestrol binds to aromatase in a manner such that rings A and C of coumestrol mimic rings A and B of steroid. These structure-function studies help us to evaluate the structural model of aromatase, and to accelerate the structure-based design for new aromatase inhibitors.
authors.affiliation: Department of Surgical Research and Division of Information Sciences, Beckman Research Institute of the City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, United States.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Hong
authors.forename: Michael
authors.initials: M
authors.lastname: Cho
authors.forename: Yate-Ching
authors.initials: YC
authors.lastname: Yuan
authors.forename: Shiuan
authors.initials: S
authors.lastname: Chen
mesh_terms: D000818:Animals; D001141:Aromatase / Q000737:chemistry* / Q000378:metabolism*; D047072:Aromatase Inhibitors / Q000378:metabolism; D016466:CHO Cells; D003375:Coumestrol / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004958:Estradiol / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D008777:Methyltestosterone / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D047072:Aromatase Inhibitors; D005452:Fluoresceins; D011994:Recombinant Proteins; C558664:dibenzylfluorescein; D004958:Estradiol; D001141:Aromatase; D003375:Coumestrol; D008777:Methyltestosterone