Structure and function of the arginine repressor-operator complex from Bacillus subtilis
Structure and function of the arginine repressor-operator complex from Bacillus subtilis
复制标题
DOI：
10.1016/j.jmb.2008.03.007
复制
发表时间：
2008-05-29
影响因子：
5.6
通讯作者：
Phillips, Simon E. V.
中科院分区：
文献类型：
--
作者：
Garnett, James A.;Marincs, Ferenc;Phillips, Simon E. V.
在许多细菌中，L精氨酸的浓度由一种转录调节因子--精氨酸抑制因子控制。在枯草芽孢杆菌中，这种转录因子被称为AHRC，在抑制和激活涉及精氨酸新陈代谢的基因方面发挥作用。它在精氨酸生物合成和分解代谢操纵子的启动子中与18个碱基的ARG盒相互作用。AHRC是一个六角体，每个亚基有两个结构域。C-末端结构域形成核心，介导亚单位间相互作用和L-精氨酸结合，而N-末端结构域包含一个带翼的螺旋-转角-螺旋DNA结合基序，排列在外围。当共抑制物L-精氨酸结合时，核心C-末端三聚体之间有类似于15度的相对旋转。在这里，我们报告了AHRC N-末端结构域二聚体(NAhrC)的X射线晶体结构，它与18BP的DNA ARG盒操作符形成络合物，分辨率提高到2.85埃。将该复合体中的N-末端结构域与自由域的N-末端结构域进行比较，发现自由域中DNA结合基序的灵活的β-翼在蛋白质-DNA复合体中形成了稳定的二聚体界面，有利于识别螺旋的正确定位。然后将它们定位以插入ARG盒的主槽的相邻转弯中，同时机翼接触次槽。在蛋白质和DNA磷酸二酯骨架之间有广泛的接触，在保守的氨基酸侧链和碱基之间有许多直接氢键。将此结构与其他AHRC组分的晶体结构相结合，我们构建了枯草杆菌生物合成ARGC操纵子上AHRC的阻遏复合体模型，并结合转录组数据分析了序列特异性和精氨酸激活的来源。(C)2008爱思唯尔有限公司。保留所有权利。
In many bacteria, the concentration of L-arginine is controlled by a transcriptional regulator, the arginine repressor. In Bacillus subtilis this transcription factor is called AhrC and has roles in both the repression and activation of the genes involved in arginine metabolism. It interacts with 18 bp ARG boxes in the promoters of arginine biosynthetic and catabolic operons. AhrC is a hexamer and each subunit has two domains. The C-terminal domains form the core, mediating inter-subunit interactions and L-arginine binding, while the N-terminal domains contain a winged helix-turn-helix DNA-binding motif and are arranged around the periphery. Upon binding of the co-repressor L-arginine there is a similar to 15 degrees relative rotation between core C-terminal trimers. Here, we report the X-ray crystal structure of a dimer of the N-terminal domains of AhrC (NAhrC) in complex with an 18 bp DNA ARG box operator, refined to 2.85 angstrom resolution. Comparison of the N-terminal domains within this complex with those of the free domain reveals that the flexible beta-wings of the DNA-binding motif in the free domain form a stable dimer interface in the protein-DNA complex, favouring correct orientation of the recognition helices. These are then positioned to insert into adjacent turns of the major groove of the ARG box, whilst the wings contact the minor groove. There are extensive contacts between the protein and the DNA phosphodiester backbone, as well as a number of direct hydrogen bonds between conserved amino acid side chains and bases. Combining this structure with other crystal structures of other AhrC components, we have constructed a model of the repression complex of AhrC at the B. subtilis biosynthetic argC operator and, along with transcriptome data, analysed the origins of sequence specificity and arginine activation. (C) 2008 Elsevier Ltd. All rights reserved.