Grandori R, Lavoie T A, Pflumm M, Tian G, Niersbach H, Maas W K, Fairman R, Carey J
Chemistry Department, Princeton University, NJ 08544-1009, USA.
J Mol Biol. 1995 Nov 24;254(2):150-62. doi: 10.1006/jmbi.1995.0607.
The arginine repressor of Escherichia coli is a classical feedback regulator, signalling the availability of L-arginine inside the cell. It differs from most other bacterial repressors in functioning as a hexamer, but structural details have been lacking and its shares no clear sequence homologies with other transcriptional regulators. Analysis of the amino acid residue sequence and proteolytic cleavage pattern of the repressor was used to identify a region predicted to house the DNA-binding function. When this protein fragment is overexpressed from a clone of the corresponding gene fragment, it represses ornithine transcarbamylase levels in vivo, and binds to the operator DNA in vitro, both in an arginine-independent manner. Sedimentation equilibrium and gel filtration indicate that the purified protein fragment is a monomer in solution. The results thus define the domain organization of the repressor at low resolution, suggesting that the N and C-terminal portions of the polypeptide chain are separated by a structural and functional border that decouples hexamerization and arginine binding from DNA binding.
大肠杆菌的精氨酸阻遏物是一种典型的反馈调节因子，可传递细胞内L-精氨酸的可用性信息。它与大多数其他细菌阻遏物不同，以六聚体形式发挥作用，但缺乏结构细节，且与其他转录调节因子没有明显的序列同源性。通过对阻遏物的氨基酸残基序列和蛋白水解切割模式进行分析，以确定一个预计具有DNA结合功能的区域。当该蛋白片段从相应基因片段的克隆中过表达时，它在体内可抑制鸟氨酸转氨甲酰酶水平，并在体外以不依赖精氨酸的方式与操纵子DNA结合。沉降平衡和凝胶过滤表明，纯化的蛋白片段在溶液中是单体。因此，这些结果在低分辨率下定义了阻遏物的结构域组织，表明多肽链的N端和C端部分被一个结构和功能边界隔开，该边界将六聚化和精氨酸结合与DNA结合解耦。
