title: Crystal structure of cambialistic superoxide dismutase from porphyromonas gingivalis.
abstract: The crystal structure of cambialistic superoxide dismutase (SOD) from Porphyromonas gingivalis, which exhibits full activity with either Fe or Mn at the active site, has been determined at 1.8-A resolution by molecular replacement and refined to a crystallographic R factor of 17.9% (Rfree 22.3%). The crystals belong to the space group P212121 (a = 75.5 A, b = 102.7 A, c = 99.6 A) with four identical subunits in the asymmetric unit. Each pair of subunits forms a compact dimer, but not a tetramer, with 222 point symmetry. Each subunit has 191 amino-acid residues most of which are visible in electron density maps, and consists of seven alpha helices and one three-stranded antiparallel beta sheet. The metal ion, a 3 : 1 mixture of Fe and Mn, is coordinated with five ligands (His27, His74, His161, Asp157, and water) arranged at the vertices of a trigonal bipyramid. Although the overall structural features, including the metal coordination geometry, are similar to those found in other single-metal containing SODs, P. gingivalis SOD more closely resembles the dimeric Fe-SODs from Escherichia coli rather than another cambialistic SOD from Propionibacterium shermanii, which itself is rather similar to other tetrameric SODs.
authors.affiliation: Yokohama Research Center, Mitsubishi Chemical Corporation, Aoba, Yokohama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sugio
authors.forename: B Y
authors.initials: BY
authors.lastname: Hiraoka
authors.forename: F
authors.initials: F
authors.lastname: Yamakura
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011092:Polyethylene Glycols / Q000737:chemistry; D016966:Porphyromonas gingivalis / Q000201:enzymology*; D011487:Protein Conformation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012996:Solutions; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D008670:Metals; D011994:Recombinant Proteins; D012996:Solutions; D011092:Polyethylene Glycols; D013482:Superoxide Dismutase