title: Characterization of a hyperthermostable Fe-superoxide dismutase from hot spring.
abstract: A new gene encoding a thermostable Fe-superoxide dismutase (tcSOD) was identified from a metagenomic library prepared from a hot spring sample. The open reading frame of tcSOD encoded a 211 amino acid protein. The recombinant protein was overexpressed in Escherichia coli and confirmed to be a Fe-SOD with a specific activity of 1,890 U/mg using the pyrogallol method. The enzyme was highly stable at 80 degrees C and retained 50% activity after heat treatment at 95 degrees C for 2 h. It showed striking stability across a wide pH span from 4 to 11. The native form of the enzyme was determined as a homotetramer by analytical ultracentrifugation and gradient native polyacrylamide gel electrophoresis. Fe(2+) was found to be important to SOD activity and to the stability of tcSOD dimer. Comparative modeling analyses of tcSOD tetramer indicate that its high thermostability is mainly due to the presence of a large number of intersubunit ion pairs and hydrogen bonds and to a decrease in solvent accessible hydrophobic surfaces.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, P.O. Box 2714, Beijing, 100080, People's Republic of China.
authors.forename: Yong-Zhi
authors.initials: YZ
authors.lastname: He
authors.forename: Ke-Qiang
authors.initials: KQ
authors.lastname: Fan
authors.forename: Cui-Juan
authors.initials: CJ
authors.lastname: Jia
authors.forename: Zhi-Jun
authors.initials: ZJ
authors.lastname: Wang
authors.forename: Wu-Bin
authors.initials: WB
authors.lastname: Pan
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.forename: Ke-Qian
authors.initials: KQ
authors.lastname: Yang
authors.forename: Zhi-Yang
authors.initials: ZY
authors.lastname: Dong
mesh_terms: D001483:Base Sequence; D001709:Biotechnology / Q000379:methods; D002681:China; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics* / Q000302:isolation & purification; D019281:Dimerization; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D015698:Genomic Library; D045482:Hot Springs; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013482:Superoxide Dismutase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D013482:Superoxide Dismutase