Structural changes in a cryo-cooled protein crystal owing to radiation damage
Structural changes in a cryo-cooled protein crystal owing to radiation damage
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DOI：
10.1107/s0907444999016261
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发表时间：
2000-03-01
影响因子：
2.2
通讯作者：
Burmeister, WP
中科院分区：
文献类型：
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作者：
Burmeister, WP
第三代X射线源的高强度，沿着蛋白质晶体低温冷却的发展。在大约100 K的温度下，已经有可能扩展晶体的衍射极限并减小它们的尺寸。然而，即使使用低温冷却的晶体，辐射损伤也成为限制因素。到目前为止，辐射损伤表现为总衍射强度的损失和温度因子的增加。研究了暴露于20 x 10（15）个光子mm（-2）范围内不同剂量的X射线后蛋白质（黑芥子酶）的结构。的变化。首次使用傅立叶差分映射和占位细化分析了辐射损伤引起的结构损伤。损伤以二硫键断裂、天冬氨酸和谷氨酸残基脱羧、酪氨酸羟基和甲硫氨酸甲硫基丢失的形式明显。同一种类的各个群体对辐射损伤的敏感性在蛋白质中各不相同。由于过量辐射剂量后晶体中存在辐解，可能会损害由结构测定产生的模型的质量。辐射诱导的结构变化可能会干扰配体结合研究或MAD数据的解释。这里报告的实验表明，有一个内在的限制，可以从一个给定的样本中提取的数据量，大小。
The high intensity of third-generation X-ray sources, along with the development of cryo-cooling of protein crystals at. temperatures around 100 K, have made it possible to extend the diffraction limit of crystals and to reduce their size. However, even with cryo-cooled crystals, radiation damage becomes a limiting factor. So far, the radiation damage has manifested itself in the form of a loss of overall diffracted intensity and an increase in the temperature factor. The structure of a protein (myrosinase) after exposure to different doses of X-rays in the region of 20 x 10(15) photons mm(-2) has been studied. The changes in the. structure owing to radiation damage were analysed using Fourier difference maps and occupancy refinement for the first time. Damage tvas obvious in the form of breakage of disulfide bonds, decarboxylation of aspartate and glutamate residues, a loss of hydroxyl groups from tyrosine and of the methylthio group of methionine. The susceptibility to radiation damage of individual groups of the same kind varies within the protein. The quality of the model resulting from structure determination might be compromised owing to the presence of radiolysis in the crystal after an excessive radiation dose. Radiation-induced structural changes may interfere with the interpretation of ligand-binding studies or MAD data. The experiments reported here suggest that there is an intrinsic limit to the amount of data which can be extracted from a sample of a given, size.