title: Crystal structure of isoflavone reductase from alfalfa (Medicago sativa L.).
abstract: Isoflavonoids play important roles in plant defense and exhibit a range of mammalian health-promoting activities. Isoflavone reductase (IFR) specifically recognizes isoflavones and catalyzes a stereospecific NADPH-dependent reduction to (3R)-isoflavanone. The crystal structure of Medicago sativa IFR with deletion of residues 39-47 has been determined at 1.6A resolution. Structural analysis, molecular modeling and docking, and comparison with the structures of other NADPH-dependent enzymes, defined the putative binding sites for co-factor and substrate and potential key residues for enzyme activity and substrate specificity. Further mutagenesis has confirmed the role of Lys144 as a catalytic residue. This study provides a structural basis for understanding the enzymatic mechanism and substrate specificity of IFRs as well as the functions of IFR-like proteins.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA. xwang@noble.org
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Wang
authors.forename: Xianzhi
authors.initials: X
authors.lastname: He
authors.forename: Jianqiao
authors.initials: J
authors.lastname: Lin
authors.forename: Hui
authors.initials: H
authors.lastname: Shao
authors.forename: Zhenzhan
authors.initials: Z
authors.lastname: Chang
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D007529:Isoflavones / Q000378:metabolism; D007700:Kinetics; D000455:Medicago sativa / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D007529:Isoflavones; D011994:Recombinant Proteins; D009249:NADP; C071072:vestitone reductase; D044925:Oxidoreductases Acting on CH-CH Group Donors