The solution structure of reduced dimeric copper zinc superoxide dismutase - The structural effects of dimerization
The solution structure of reduced dimeric copper zinc superoxide dismutase - The structural effects of dimerization
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DOI：
10.1046/j.1432-1327.2002.02840.x
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发表时间：
2002-04-01
期刊：
影响因子：
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通讯作者：
Viezzoli, MS
中科院分区：
文献类型：
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作者：
Banci, L;Bertini, I;Viezzoli, MS
采用（13）C、（15）N和70% (2)H标记样品，测定了306种氨基酸的Cu-2 Zn-2超氧化物歧化酶（SOD）的溶液结构。使用了2,885个有意义的noe，其中96个亚基间角和115个二面角提供了30个构象家族，主原子和重原子的rmsd分别为0.78 +/- 0.11和1.15 +/- 0.09埃。当计算每个亚基的rmsd时，主原子和重原子的rmsd值分别降至0.65 +/- 0.09和1.08 +/- 0.11埃。这两个亚基在核磁共振时间尺度上是相同的，与x射线结构不同，x射线结构显示了两个亚基之间以及单位细胞中不同分子之间的结构差异。二级结构的元素，即8个β片，与x射线结构中的元素相同，并且定义良好。奇循环（I， III和V）和位于亚基界面的循环II被很好地分解。相反，循环IV和VI表现出一定的紊乱。活性腔的残基是明确的，而在x射线结构的不同亚基内，一些亚基是无序的或在不同的x射线结构测定中显示不同的取向。铜(I)离子及其配体是明确的。因此，该结构代表了与蛋白质结构-功能分析相关的溶液中定义良好的模型。单体突变体的溶液结构与现有结构的比较表明，亚基-亚基相互作用增加了环路II的顺序。这就产生了对野生型酶的酶功能最优的结构和动态特性的诱导结果。37-43和89-95区构成环III和V以及β桶的初始部分，在家族性肌萎缩性侧索硬化症（FALS）相关蛋白中显示出一些突变，它们具有相当广泛的氢键网络，这可能是它们低流动性的原因。最后，将关键Arg143残基的构象与其他二聚体和单体结构以及最近报道的ccs -超氧化物歧化酶（SOD）复合物的结构进行了比较。
The solution structure of homodimeric Cu-2 Zn-2 superoxide dismutase (SOD) of 306 aminoacids was determined on a (13) C, (15) N and 70% (2) H labeled sample. Two-thousand eight-hundred and five meaningful NOEs were used, of which 96 intersubunit, and 115 dihedral angles provided a family of 30 conformers with an rmsd from the average of 0.78 +/- 0.11 and 1.15 +/- 0.09 Angstrom for the backbone and heavy atoms, respectively. When the rmsd is calculated for each subunit, the values drop to 0.65 +/- 0.09 and 1.08 +/- 0.11 Angstrom for the backbone and heavy atoms, respectively.The two subunits are identical on the NMR time scale, at variance with the X-ray structures that show structural differences between the two subunits as well as between different molecules in the unit cell. The elements of secondary structure, i.e. eight beta sheets, are the same as in the X-ray structures and are well defined. The odd loops (I, III and V) are well resolved as well as loop II located at the subunit interface. On the contrary, loops IV and VI show some disorder. The residues of the active cavity are well defined whereas within the various subunits of the X-ray structure some are disordered or display different orientation in different X-ray structure determinations. The copper(I) ion and its ligands are well defined. This structure thus represents a well defined model in solution relevant for structure-function analysis of the protein. The comparison between the solution structure of monomeric mutants and the present structure shows that the subunit-subunit interactions increase the order in loop II. This has the consequences of inducing the structural and dynamic properties that are optimal for the enzymatic function of the wild-type enzyme. The regions 37-43 and 89-95, constituting loops III and V and the initial part of the beta barrel and showing several mutations in familial amyotrophis lateral sclerosis (FALS)-related proteins have a quite extensive network of H-bonds that may account for their low mobility. Finally, the conformation of the key Arg143 residue is compared to that in the other dimeric and monomeric structures as well as in the recently reported structure of the CCS-superoxide dismutase (SOD) complex.