title: Cloning of a gene encoding flavin reductase coupling with dibenzothiophene monooxygenase through coexpression screening using indigo production as selective indication.
abstract: The thermophilic dibenzothiophene (DBT)-desulfurizing bacterium, Bacillus subtilis WU-S2B, possesses the ability to convert DBT to 2-hydroxybiphenyl with the release of inorganic sulfur over a wide temperature range up to 50 degrees C. The conversion is initiated by consecutive sulfur atom-specific oxidations by two monooxygenases, and flavin reductase is essential in combination with these flavin-dependent monooxygenases. The recombinant Escherichia coli cells expressing the DBT monooxygenase gene (bdsC) from B. subtilis WU-S2B also oxidize indole to blue pigment indigo in the presence of a heterologous flavin reductase. Thus, to clone a gene encoding flavin reductase from B. subtilis WU-S2B, indigo production by coexpression of the gene with bdsC in E. coli was used as a selection. Using this method, the corresponding gene (frb) was obtained from a recombinant strain forming a blue colony due to indigo production on a nutrient agar plate, and it was confirmed that this gene product Frb exhibited flavin reductase activity. The deduced amino acid sequence of frb consists of 174 amino acid residues and shares 61% identity with that of nitroreductase (YwrO) of Bacillus amyloliquefaciens. In addition, coexpression of frb with the DBT-desulfurization genes (bdsABC) from B. subtilis WU-S2B was critical for high DBT-desulfurizing ability over a wide temperature range of 20-55 degrees C. This coexpression screening using indigo production as selective indication may be widely applicable for cloning novel genes encoding either component of flavin reductase or flavin-dependent monooxygenase which efficiently couples with the other component in two-component monooxygenases.
authors.affiliation: Department of Applied Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Furuya
authors.forename: Shusuke
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ishii
authors.forename: Kuniki
authors.initials: K
authors.lastname: Kino
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Kirimura
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D001669:Biochemical Phenomena; D001671:Biochemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D038181:FMN Reductase / Q000235:genetics*; D005415:Flavins / Q000378:metabolism; D007203:Indigo Carmine; D007211:Indoles / Q000378:metabolism*; D008956:Models, Chemical; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D010860:Pigments, Biological; D010957:Plasmids / Q000378:metabolism; D013696:Temperature; D013876:Thiophenes / Q000378:metabolism
chemical_list: D001713:Biphenyl Compounds; D005415:Flavins; D007211:Indoles; D010860:Pigments, Biological; D013876:Thiophenes; D004247:DNA; C004369:2-phenylphenol; D007203:Indigo Carmine; D010088:Oxidoreductases; D038181:FMN Reductase; C090100:dibenzothiophene monooxygenase; C016366:dibenzothiophene