Watanabe Nobuhisa, Kitago Yu, Tanaka Isao, Wang Jia wei, Gu Yuan xin, Zheng Chao de, Fan Hai fu
Graduate School of Science, Hokkaido University, Sapporo 0600810, Japan.
Acta Crystallogr D Biol Crystallogr. 2005 Nov;61(Pt 11):1533-40. doi: 10.1107/S0907444905028416. Epub 2005 Oct 19.
Phasing of the crystal structures of four standard proteins (lysozyme, trypsin, glucose isomerase and thaumatin) and a novel 69 kDa protein from Thermus thermophilus, TT0570, was performed using the single-wavelength anomalous diffraction of S atoms intrinsically present within the native protein molecules. To utilize the sulfur anomalous diffraction, the data sets were collected using the loopless data-collection method with chromium Kalpha X-rays of wavelength 2.29 A. Three phasing methods, MLPHARE, SHARP and OASIS-2004, were tested in combination with the DM or SOLOMON density-modification method. The results showed that the solvent contents are still an important factor for phasing with the S-SAD method, even when longer wavelength Cr Kalpha radiation is used. Of the three procedures, the improved direct phasing of OASIS-2004 with its implemented fragment feedback to the direct-method probability calculation gave the best results in determining the initial phases. For all five proteins, almost the entire models could be built automatically.
利用天然蛋白质分子中固有的S原子的单波长反常衍射，对四种标准蛋白质（溶菌酶、胰蛋白酶、葡萄糖异构酶和奇异果甜蛋白）以及嗜热栖热菌的一种新型69 kDa蛋白质TT0570的晶体结构进行了相位测定。为了利用硫反常衍射，使用波长为2.29 Å的铬Kα X射线，通过无环数据收集方法收集数据集。测试了三种相位测定方法MLPHARE、SHARP和OASIS - 2004，并结合DM或SOLOMON密度修正方法。结果表明，即使使用更长波长的铬Kα辐射，溶剂含量仍是S-SAD方法相位测定的一个重要因素。在这三种方法中，改进后的OASIS - 2004直接相位测定法及其对直接法概率计算的片段反馈在确定初始相位方面给出了最佳结果。对于所有五种蛋白质，几乎整个模型都可以自动构建。
