X-ray damage to the Mn4Ca complex in single crystals of photosystem II:: A case study for metalloprotein crystallography
X-ray damage to the Mn4Ca complex in single crystals of photosystem II:: A case study for metalloprotein crystallography
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DOI：
10.1073/pnas.0505207102
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发表时间：
2005-08-23
影响因子：
11.1
通讯作者：
Yachandra, VK
中科院分区：
文献类型：
--
作者：
Yano, J;Kern, J;Yachandra, VK
X-射线吸收光谱法被用来测量由暴露于X-射线的光系统II的单晶中的Mn 4Ca活性位点作为剂量和能量的X-射线，温度和时间的函数所造成的损害。这些研究表明，X射线晶体学结构测定所用的条件会对金属位点结构造成严重损害。的X-射线吸收光谱表明，从一个是一个特征的高价Mn-4（III 2，IV 2），氧桥Mn 4Ca簇的Mn（II）在水溶液中的结构变化。这种对金属位点的损伤发生在比导致蛋白质活性丧失的剂量低一个数量级以上的剂量下，并且通常被认为对蛋白质晶体学是安全的。这些结果建立了适用于氧化还原活性金属蛋白的定量X射线剂量参数。这个案例研究表明，通过光谱技术仔细评估活性位点的结构完整性可以验证来自晶体学的结构，并且在基于高分辨率X射线晶体结构进行金属蛋白质的结构-功能相关性之前，它可以是一种有价值的补充方法。
X-ray absorption spectroscopy was used to measure the damage caused by exposure to x-rays to the Mn4Ca active site in single crystals of photosystem II as a function of dose and energy of x-rays, temperature, and time. These studies reveal that the conditions used for structure determination by x-ray crystallography cause serious damage specifically to the metal-site structure. The x-ray absorption spectra show that the structure changes from one that is characteristic of a high-valent Mn-4(III2,IV2), oxo-bridged Mn4Ca cluster to that of Mn(II) in aqueous solution. This damage to the metal site occurs at a dose that is more than one order of magnitude lower than the dose that results in loss of diffractivity and is commonly considered safe for protein crystallography. These results establish quantitative x-ray dose parameters that are applicable to redox-active metalloproteins. This case study shows that a careful evaluation of the structural intactness of the active site(s) by spectroscopic techniques can validate structures derived from crystallography and that it can be a valuable complementary method before structure-function correlations of metalloproteins can be made on the basis of high-resolution x-ray crystal structures.