The first structure of a cold-adapted superoxide dismutase (SOD): biochemical and structural characterization of iron SOD from Aliivibrio salmonicida.
Superoxide dismutases (SODs) are metalloenzymes that catalyse the dismutation of the superoxide radical anion into O(2) and H(2)O(2) in a two-step reaction. The crystal structure of the iron superoxide dismutase from the cold-adapted and fish-pathogenic bacterium Aliivibrio salmonicida (asFeSOD) has been determined and refined to 1.7 A resolution. The protein has been characterized and compared with the closely related homologous iron superoxide dismutase from the mesophilic Escherichia coli (ecFeSOD) in an attempt to rationalize its environmental adaptation. ecFeSOD shares 75% identity with asFeSOD. Compared with the mesophilic FeSOD, the psychrophilic FeSOD has distinct temperature differences in residual activity and thermostability that do not seem to be related to structural differences such as intramolecular or intermolecular ion bonds, hydrogen bonds or cavity sizes. However, an increased net negative charge on the surface of asFeSOD may explain its lower thermostability compared with ecFeSOD. Activity measurements and differential scanning calorimetry measurements revealed that the psychrophilic asFeSOD had a thermostability that was significantly higher than the optimal growth temperature of the host organism.
Pedersen
Hege Lynum
HL
Department of Molecular Biotechnology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
Willassen
Nils Peder
NP
Leiros
Ingar
I
D000222:Adaptation, Physiological; D044165:Aliivibrio salmonicida / Q000201:enzymology*; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D004795:Enzyme Stability / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology; D048388:Gadiformes; D007501:Iron / Q000737:chemistry*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000302:isolation & purification; D013816:Thermodynamics
D001426:Bacterial Proteins; D007501:Iron; D013482:Superoxide Dismutase