title: Crystal structure of dimeric flavodoxin from Desulfovibrio gigas suggests a potential binding region for the electron-transferring partner.
abstract: Flavodoxins, which exist widely in microorganisms, have been found in various pathways with multiple physiological functions. The flavodoxin (Fld) containing the cofactor flavin mononucleotide (FMN) from sulfur-reducing bacteria Desulfovibrio gigas (D. gigas) is a short-chain enzyme that comprises 146 residues with a molecular mass of  15 kDa and plays important roles in the electron-transfer chain. To investigate its structure, we purified this Fld directly from anaerobically grown D. gigas cells. The crystal structure of Fld, determined at resolution 1.3 Å, is a dimer with two FMN packing in an orientation head to head at a distance of 17 Å, which generates a long and connected negatively charged region. Two loops, Thr59-Asp63 and Asp95-Tyr100, are located in the negatively charged region and between two FMN, and are structurally dynamic. An analysis of each monomer shows that the structure of Fld is in a semiquinone state; the positions of FMN and the surrounding residues in the active site deviate. The crystal structure of Fld from D. gigas agrees with a dimeric form in the solution state. The dimerization area, dynamic characteristics and structure variations between monomers enable us to identify a possible binding area for its functional partners.
authors: Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan. cjchen@nsrrc.org.tw.
authors: Yin-Cheng
authors: YC
authors: Hsieh
authors: Tze Shyang
authors: TS
authors: Chia
authors: Hoong-Kun
authors: HK
authors: Fun
authors: Chun-Jung
authors: CJ
authors: Chen
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D018360:Crystallography, X-Ray; D045286:Desulfovibrio gigas / Q000201:enzymology* / Q000235:genetics; D004579:Electron Transport; D005486:Flavin Mononucleotide / Q000737:chemistry / Q000378:metabolism; D005418:Flavodoxin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D005418:Flavodoxin; D005486:Flavin Mononucleotide