Stallings W C, Pattridge K A, Strong R K, Ludwig M L
J Biol Chem. 1984 Sep 10;259(17):10695-9.
The crystal structure of a tetrameric manganese superoxide dismutase from a thermophilic bacterium, Thermus thermophilus HB8, has been determined at 4.4-A resolution by local averaging of electron density maps calculated by isomorphous replacement. The spatial arrangement of the principal secondary structural features of iron superoxide dismutase is conserved in manganese dismutase. The structural homology is displayed by orienting the polypeptide chain of Escherichia coli Fe dismutase in the electron density map of Mn dismutase. Densities corresponding to bound Mn3+ occur at locations equivalent to the Fe3+ positions in iron dismutase, indicating one metal binding site per chain, or four sites per tetramer. The Mn tetramer, with 222 symmetry, is approximately rectangular in shape and appears to be constructed with only two unique interfaces. One set of interchain contacts closely resembles the dimer interface of Fe dismutase, but the other interface utilizes an inserted polypeptide segment that has no equivalent in Fe dismutase.
嗜热栖热菌HB8来源的四聚体锰超氧化物歧化酶的晶体结构，已通过同晶置换法计算的电子密度图的局部平均，在4.4埃分辨率下得以确定。铁超氧化物歧化酶主要二级结构特征的空间排列在锰超氧化物歧化酶中得以保留。通过在锰超氧化物歧化酶的电子密度图中定位大肠杆菌铁超氧化物歧化酶的多肽链，展示了结构同源性。与结合的Mn3+相对应的密度出现在与铁超氧化物歧化酶中铁3+位置相当的位置，表明每条链有一个金属结合位点，或每个四聚体有四个位点。具有222对称性的锰四聚体近似矩形，似乎仅由两个独特的界面构成。一组链间接触与铁超氧化物歧化酶的二聚体界面非常相似，但另一个界面利用了一个在铁超氧化物歧化酶中没有对应物的插入多肽片段。
