中文摘要：

RecQ解旋酶是生物分子代谢过程中重要的大分子物质,对保持遗传物质的稳定性具有重要作用。通过PCR从E.coli DH5α菌株的基因组中扩增出E.coli RecQ基因并克隆入原核表达载体pET24a（＋）中,转化大肠杆菌E.coli BL21（DE3）,IPTG诱导表达,目的蛋白主要以可溶形式存在于菌体中。优化表达条件后,经镍柱螯合亲和层析纯化获得纯度大于90%的目标蛋白质,应用生物化学和生物物理学技术研究E.coli RecQ 解旋酶的生物学活性。结果表明,E.coli RecQ解旋酶具有DNA依赖性和蛋白浓度依赖性的ATP水解活性。在等蛋白质浓度下,E.coli RecQ酶结合DNA活性强弱依次为开叉dsDNA, ssDNA,平末端dsDNA。其还具有ATP依赖的dsDNA解链活性和时间依赖的DNA退火活性。实验为RecQ解旋酶家族其他重要成员的活性功能研究提供了理论依据和重要参考。

英文摘要：

RecQ helicases are one of the most important macromolecules in the process of molecular metabolism. They play essential roles in maintaining the stability of the genetic materials in cells. The DNA corresponding to the coding sequence of the E.coli RecQ helicase gene was amplified by PCR from the chromosome DNA of Escherichia coli DH5α. The amplified product was subcloned into the expression vector pET24a（＋）. The recombinant protein was induced to express in Escherichia coli BL21（DE3） with IPTG at low temperature. E. coli RecQ helicase was with above 90% purity and good solubility was obtained in vitro. With biochemical and biophysical techniques, E. coli RecQ helicase was shown to have DNA-dependent ATPase activity in concentration-dependent manner. It was easier to bind forked ds DNA than ssDNA and blunt end dsDNA in the same protein concentration. E.coli RecQ helicase also has ATP-dependent DNA unwinding activity and time-dependent DNA annealing activity. These results are helpful to study the structures and functions of other members of the RecQ family helicases.