Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806.
J Biol Chem. 2010 Apr 30;285(18):14020-30. doi: 10.1074/jbc.M109.100248. Epub 2010 Feb 23.
Quorum sensing has been implicated as an important global regulatory system controlling the expression of numerous virulence factors in bacterial pathogens. SmcR, a homologue of Vibrio harveyi LuxR, has been proposed as a quorum-sensing master regulator of Vibrio vulnificus, an opportunistic human pathogen. Previous studies demonstrated that SmcR is essential for the survival and pathogenesis of V. vulnificus, indicating that inhibiting SmcR is an attractive approach to combat infections by the bacteria. Here, we determined the crystal structure of SmcR at 2.1 A resolution. The protein structure reveals a typical TetR superfamily fold consisting of an N-terminal DNA binding domain and a C-terminal dimerization domain. In vivo and in vitro functional analysis of the dimerization domain suggested that dimerization of SmcR is vital for its biological regulatory function. The N-terminal DNA recognition and binding residues were assigned based on the protein structure and the results of in vivo and in vitro mutagenesis experiments. Furthermore, protein-DNA interaction experiments suggested that SmcR may have a sophisticated mechanism that enables the protein to recognize each of its many target operators with different affinities.
群体感应被认为是一种重要的全球调控系统，控制着细菌病原体中许多毒力因子的表达。SmcR 是 Harveyi Vibrio LuxR 的同源物，被提议作为弧菌 Vulnificus 的群体感应主调控因子，弧菌 Vulnificus 是一种机会性人类病原体。先前的研究表明 SmcR 对弧菌 Vulnificus 的存活和发病机制是必不可少的，这表明抑制 SmcR 是对抗细菌感染的一种有吸引力的方法。在这里，我们确定了 SmcR 的晶体结构，分辨率为 2.1A。蛋白质结构揭示了一个典型的 TetR 超家族折叠，由一个 N 端 DNA 结合域和一个 C 端二聚化域组成。体内和体外功能分析表明二聚化对于 SmcR 的生物学调节功能至关重要。根据蛋白质结构和体内和体外诱变实验的结果，确定了 N 端 DNA 识别和结合残基。此外，蛋白质-DNA 相互作用实验表明 SmcR 可能具有一种复杂的机制，使该蛋白能够以不同的亲和力识别其许多靶标操作子中的每一个。
