title: An Fe-S cluster in the conserved Cys-rich region in the catalytic subunit of FAD-dependent dehydrogenase complexes.
abstract: Several bacterial flavin adenine dinucleotide (FAD)-harboring dehydrogenase complexes comprise three distinct subunits: a catalytic subunit with FAD, a cytochrome c subunit containing three hemes, and a small subunit. Owing to the cytochrome c subunit, these dehydrogenase complexes have the potential to transfer electrons directly to an electrode. Despite various electrochemical applications and engineering studies of FAD-dependent dehydrogenase complexes, the intra/inter-molecular electron transfer pathway has not yet been revealed. In this study, we focused on the conserved Cys-rich region in the catalytic subunits using the catalytic subunit of FAD dependent glucose dehydrogenase complex (FADGDH) as a model, and site-directed mutagenesis and electron paramagnetic resonance (EPR) were performed. By co-expressing a hitch-hiker protein (γ-subunit) and a catalytic subunit (α-subunit), FADGDH γα complexes were prepared, and the properties of the catalytic subunit of both wild type and mutant FADGDHs were investigated. Substitution of the conserved Cys residues with Ser resulted in the loss of dye-mediated glucose dehydrogenase activity. ICP-AEM and EPR analyses of the wild-type FADGDH catalytic subunit revealed the presence of a 3Fe-4S-type iron-sulfur cluster, whereas none of the Ser-substituted mutants showed the EPR spectrum characteristic for this cluster. The results suggested that three Cys residues in the Cys-rich region constitute an iron-sulfur cluster that may play an important role in the electron transfer from FAD (intra-molecular) to the multi-heme cytochrome c subunit (inter-molecular) electron transfer pathway. These features appear to be conserved in the other three-subunit dehydrogenases having an FAD cofactor.
authors.affiliation: Department of Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture & Technology, Koganei, Tokyo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Shiota
authors.affiliation: International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Yamazaki
authors.affiliation: Department of Chemistry, Missouri State University, Springfield, MO, United States.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yoshimatsu
authors.affiliation: Ultizyme International Ltd., Meguro, Tokyo, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Kojima
authors.affiliation: Department of Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture & Technology, Koganei, Tokyo, Japan.
authors.forename: Wakako
authors.initials: W
authors.lastname: Tsugawa
authors.affiliation: Department of Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture & Technology, Koganei, Tokyo, Japan.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ferri
authors.affiliation: Department of Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture & Technology, Koganei, Tokyo, Japan; Ultizyme International Ltd., Meguro, Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Sode
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D017124:Conserved Sequence; D003545:Cysteine; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D042843:Glucose 1-Dehydrogenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007501:Iron; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D013455:Sulfur
chemical_list: D005182:Flavin-Adenine Dinucleotide; D013455:Sulfur; D007501:Iron; D042843:Glucose 1-Dehydrogenase; D003545:Cysteine
keywords: Direct electron transfer; FAD; FAD-dependent dehydrogenase; Fe–S cluster; Glucose dehydrogenase