Viadiu Hector, Vanamee Eva Scheuring, Jacobson Eric M, Schildkraut Ira, Aggarwal Aneel K
Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY 10029, USA.
Acta Crystallogr D Biol Crystallogr. 2003 Aug;59(Pt 8):1493-5. doi: 10.1107/s0907444903011910. Epub 2003 Jul 23.
The SfiI endonuclease from Streptomyces fimbriatus (EC 3.1.21.4) is a tetrameric enzyme that binds simultaneously to two recognition sites and cleaves both sites concertedly. It serves as a good model system for studying both specificity and cooperative DNA binding. Crystals of the enzyme were obtained by the hanging-drop vapor-diffusion method in complex with a 21-mer oligonucleotide. The crystals are trigonal, with unit-cell parameters a = b = 85.7, c = 202.6 A, and diffract to 2.6 A resolution on a rotating-anode X-ray generator. Preliminary X-ray analysis reveals the space group to be either P3(1)21 or P3(2)21. Interestingly, the crystals change to space group P6(1)22, with unit-cell parameters a = b = 85.5, c = 419.6 A, when the selenomethionyl (SeMet) derivative of the enzyme is co-crystallized with the same DNA. Phase information is currently being derived from this SeMet SfiI-DNA complex.
来自链霉菌（Streptomyces fimbriatus）的SfiI核酸内切酶（EC 3.1.21.4）是一种四聚体酶，它能同时结合两个识别位点并协同切割这两个位点。它是研究特异性和协同DNA结合的良好模型系统。通过悬滴气相扩散法获得了该酶与21聚体寡核苷酸复合物的晶体。晶体为三方晶系，晶胞参数a = b = 85.7，c = 202.6 Å，在旋转阳极X射线发生器上可衍射至2.6 Å分辨率。初步X射线分析表明空间群为P3(1)21或P3(2)21。有趣的是，当该酶的硒代甲硫氨酸（SeMet）衍生物与相同的DNA共结晶时，晶体转变为空间群P6(1)22，晶胞参数a = b = 85.5，c = 419.6 Å。目前正在从这种SeMet SfiI-DNA复合物中获取相位信息。
