Crystal structure of the cambialistic superoxide dismutase from Aeropyrum pernix K1 – insights into the enzyme mechanism and stability
Crystal structure of the cambialistic superoxide dismutase from Aeropyrum pernix K1 – insights into the enzyme mechanism and stability
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DOI：
10.1111/j.1742-4658.2010.07977.x
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发表时间：
2011-02
期刊：
影响因子：
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通讯作者：
Tsutomu Nakamura;K. Torikai;K. Uegaki;J. Morita;Kodai Machida;Atsushi Suzuki;Y. Kawata
中科院分区：
文献类型：
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作者：
Tsutomu Nakamura;K. Torikai;K. Uegaki;J. Morita;Kodai Machida;Atsushi Suzuki;Y. Kawata
Pernix Aeropyrum K1是一种嗜热性好氧细菌，能产生一种在锰或铁存在的情况下具有活性的诱生超氧化物歧化酶。分别以1.56、1.35和1.48的分辨率测定了Pernix超氧化物歧化酶的apo、Mn和Fe结合形式的晶体结构。整个结构由紧凑的同源四聚体组成。用分析超速离心法确定了溶液中的四聚体缔合。在锰结合形式中，金属与五个配体形成三方双锥配位：四个侧链原子和一个水氧。一个天冬氨酸和两个组氨酸侧链连接到赤道平面上的中心金属上。在铁结合形式中，在赤道平面上的两个组氨酸之间观察到一个额外的水分子，该金属与六个配体以八面体配位。额外的水占据了假定的超氧化物结合位置。将该酶的热稳定性与离子对含量较少的嗜热菌Thermus thermophilus的超氧化物歧化酶进行了比较。在水溶液中，两种酶的稳定性基本相同，但在含有乙二醇或乙醇的溶液中，Pernix酶的热稳定性显著高于嗜热链霉菌的酶。这表明优势离子对使Pernix超氧化物歧化酶对有机介质具有耐受性。
Aeropyrum pernix K1, an aerobic hyperthermophilic archaeon, produces a cambialistic superoxide dismutase that is active in the presence of either of Mn or Fe. The crystal structures of the superoxide dismutase from A. pernix in the apo, Mn‐bound and Fe‐bound forms were determined at resolutions of 1.56, 1.35 and 1.48 Å, respectively. The overall structure consisted of a compact homotetramer. Analytical ultracentrifugation was used to confirm the tetrameric association in solution. In the Mn‐bound form, the metal was in trigonal bipyramidal coordination with five ligands: four side chain atoms and a water oxygen. One aspartate and two histidine side chains ligated to the central metal on the equatorial plane. In the Fe‐bound form, an additional water molecule was observed between the two histidines on the equatorial plane and the metal was in octahedral coordination with six ligands. The additional water occupied the postulated superoxide binding site. The thermal stability of the enzyme was compared with superoxide dismutase from Thermus thermophilus, a thermophilic bacterium, which contained fewer ion pairs. In aqueous solution, the stabilities of the two enzymes were almost identical but, when the solution contained ethylene glycol or ethanol, the A. pernix enzyme had significantly higher thermal stability than the enzyme from T. thermophilus. This suggests that dominant ion pairs make A. pernix superoxide dismutase tolerant to organic media.