Alekshun M N, Kim Y S, Levy S B
Center for Adaptation Genetics and Drug Resistance and the Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
Mol Microbiol. 2000 Mar;35(6):1394-404. doi: 10.1046/j.1365-2958.2000.01802.x.
MarR, the negative regulator of the Escherichia coli multiple antibiotic resistance (marRAB) operon, is a member of a newly recognized family of regulatory proteins. The amino acid sequences of these proteins do not display any apparent homologies to the DNA binding domains of prokaryotic transcription regulators and a DNA binding motif for any one of the MarR homologues is currently unknown. In order to define regions of MarR required for DNA binding, mutant repressors, selected based on their ability to interfere with (negatively complement) the activity of wild-type MarR, were isolated. As determined using gel mobility shift assays, 13 out of 14 negative complementing mutants tested were unable to bind DNA in vitro. Three negative complementing alleles presumably specify truncated repressors and one of these proteins, a 120 residue MarR, can bind DNA in vitro. Most of the negative complementing mutations were clustered within two areas of MarR with features related to a helix-turn-helix DNA binding motif. These regions are presumed to be required for the DNA binding activity of the repressor.
MarR是大肠杆菌多重抗生素耐药性（marRAB）操纵子的负调控因子，属于一个新发现的调控蛋白家族成员。这些蛋白质的氨基酸序列与原核转录调节因子的DNA结合结构域没有任何明显的同源性，目前尚不清楚任何一种MarR同源物的DNA结合基序。为了确定MarR中DNA结合所需的区域，我们分离了基于其干扰（负互补）野生型MarR活性的能力而选择的突变阻遏物。使用凝胶迁移率变动分析确定，所测试的14个负互补突变体中有13个在体外无法结合DNA。三个负互补等位基因可能指定了截短的阻遏物，其中一种蛋白质，即120个残基的MarR，能够在体外结合DNA。大多数负互补突变集中在MarR的两个区域内，这些区域具有与螺旋-转角-螺旋DNA结合基序相关的特征。这些区域被认为是阻遏物DNA结合活性所必需的。
