Ramagopal Udupi A, Dauter Miroslawa, Dauter Zbigniew
Synchrotron Radiation Research Section, National Cancer Institute, Brookhaven National Laboratory, Building 725A-X9, Upton, NY 11973, USA.
Acta Crystallogr D Biol Crystallogr. 2003 Jun;59(Pt 6):1020-7. doi: 10.1107/s0907444903007467. Epub 2003 May 23.
Recent years have witnessed significant advancements in X-ray data-acquisition techniques and phasing algorithms, which have made possible the successful use of a very small anomalous diffraction signal for the solution of crystal structures of macromolecules. Two crystal structures, a 44 kDa glucose isomerase containing nine sulfurs and a 33 kDa xylanase containing five sulfurs, have been solved from single-wavelength anomalous data using widely available methods and programs. These two enzymes contain less sulfur than most proteins in the bacterial or eukaryotic proteomes, providing a Bijvoet ratio of about 0.6%. For glucose isomerase the automatically interpretable electron-density maps could be obtained at high as well as low resolution. The S-SAD approach relies on the anomalous signal of sulfur naturally occurring in proteins and alleviates all need for sample derivatization. It may therefore be applicable to all protein crystals able to provide accurate diffraction data.
近年来，X射线数据采集技术和相位算法取得了重大进展，这使得利用非常小的反常衍射信号成功解析大分子晶体结构成为可能。使用广泛可用的方法和程序，从单波长反常数据中解析出了两种晶体结构，一种是含有九个硫原子的44 kDa葡萄糖异构酶，另一种是含有五个硫原子的33 kDa木聚糖酶。这两种酶所含的硫比细菌或真核蛋白质组中的大多数蛋白质都少，提供了约0.6%的比旋光率。对于葡萄糖异构酶，在高分辨率和低分辨率下都可以获得可自动解释的电子密度图。单波长硫反常散射（S-SAD）方法依赖于蛋白质中天然存在的硫的反常信号，无需对样品进行衍生化处理。因此，它可能适用于所有能够提供准确衍射数据的蛋白质晶体。
