Pedersen Hege Lynum, Willassen Nils Peder, Leiros Ingar
Department of Molecular Biotechnology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2009 Feb 1;65(Pt 2):84-92. doi: 10.1107/S1744309109001110. Epub 2009 Jan 31.
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.
超氧化物歧化酶（SODs）是金属酶，可通过两步反应催化超氧阴离子自由基歧化为O₂和H₂O₂。已确定并将来自冷适应且具有鱼类致病性的细菌杀鲑气单胞菌（Aliivibrio salmonicida）的铁超氧化物歧化酶（asFeSOD）的晶体结构精修至1.7 Å分辨率。对该蛋白质进行了表征，并与来自嗜温大肠杆菌（ecFeSOD）的密切相关的同源铁超氧化物歧化酶进行了比较，以试图解释其环境适应性。ecFeSOD与asFeSOD的同一性为75%。与嗜温FeSOD相比，嗜冷FeSOD在残余活性和热稳定性方面存在明显的温度差异，这些差异似乎与诸如分子内或分子间离子键、氢键或腔大小等结构差异无关。然而，asFeSOD表面净负电荷的增加可能解释了其与ecFeSOD相比热稳定性较低的原因。活性测量和差示扫描量热法测量表明，嗜冷asFeSOD的热稳定性明显高于宿主生物体的最佳生长温度。
