Wang Q, Calvo J M
Section of Genetics and Development, Cornell University, Ithaca, NY 14853.
EMBO J. 1993 Jun;12(6):2495-501. doi: 10.1002/j.1460-2075.1993.tb05904.x.
Lrp (Leucine-responsive regulatory protein) is a global regulatory protein that controls the expression of many operons in Escherichia coli. One of those operons, ilvIH, contains six Lrp binding sites located within a several hundred base pair region upstream of the promoter region. Analysis of the binding of Lrp to a set of circularly permuted DNA fragments from this region indicates that Lrp induces DNA bending. The results of DNase I footprinting experiments suggest that Lrp binding to this region facilitates the formation of a higher-order nucleoprotein structure. To define more precisely the degree of bending associated with Lrp binding, one or two binding sites were separately cloned into a pBend vector and analyzed. Lrp induced a bend of approximately 52 degrees upon binding to a single binding site, and the angle of bending is increased to at least 135 degrees when Lrp binds to two adjacent sites. Lrp-induced DNA bending, and a natural sequence-directed bend that exists within ilvIH DNA, may be architectural elements that facilitate the assembly of a nucleoprotein complex.
Lrp（亮氨酸应答调节蛋白）是一种全局性调节蛋白，可控制大肠杆菌中许多操纵子的表达。其中一个操纵子ilvIH在启动子区域上游几百个碱基对区域内含有六个Lrp结合位点。对Lrp与该区域一组环形排列的DNA片段结合的分析表明，Lrp可诱导DNA弯曲。DNase I足迹实验结果表明，Lrp与该区域的结合促进了高阶核蛋白结构的形成。为了更精确地确定与Lrp结合相关的弯曲程度，将一个或两个结合位点分别克隆到pBend载体中并进行分析。Lrp与单个结合位点结合时可诱导约52度的弯曲，当Lrp与两个相邻位点结合时，弯曲角度增加到至少135度。Lrp诱导的DNA弯曲以及ilvIH DNA中存在的天然序列导向弯曲可能是促进核蛋白复合物组装的结构元件。
