title: Crystal structure of an apo form of Shigella flexneri ArsH protein with an NADPH-dependent FMN reductase activity.
abstract: The arsH gene or its homologs are a frequent part of the arsenic resistance system in bacteria and eukaryotes. Although a specific biological function of the gene product is unknown, the ArsH protein was annotated as a member of the NADPH-dependent FMN reductase family based on a conserved (T/S)XRXXSX(T/S) fingerprint motif common for FMN binding proteins. Presented here are the first crystal structure of an ArsH protein from Shigella flexneri refined at 1.7 A resolution and results of enzymatic activity assays that revealed a strong NADPH-dependent FMN reductase and low azoreductase activities. The ArsH apo protein has an alpha/beta/alpha-fold typical for FMN binding proteins. The asymmetric unit consists of four monomers, which form a tetramer. Buried surface analysis suggests that this tetramer is likely to be the relevant biological assembly. Dynamic light scattering experiments are consistent with this hypothesis and show that ArsH in solution at room temperature does exist predominantly in the tetrameric form.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Ivan I
authors.initials: II
authors.lastname: Vorontsov
authors.forename: George
authors.initials: G
authors.lastname: Minasov
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Brunzelle
authors.forename: Ludmilla
authors.initials: L
authors.lastname: Shuvalova
authors.forename: Olga
authors.initials: O
authors.lastname: Kiryukhina
authors.forename: Frank R
authors.initials: FR
authors.lastname: Collart
authors.forename: Wayne F
authors.initials: WF
authors.lastname: Anderson
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D038181:FMN Reductase / Q000378:metabolism*; D008027:Light; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009249:NADP / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D012763:Shigella flexneri / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D009249:NADP; D038181:FMN Reductase