Wehland M, Bernhard F
Freie Universität Berlin, Institut für Kristallographie, Takustrasse 6, D-14195 Berlin, Germany.
J Biol Chem. 2000 Mar 10;275(10):7013-20. doi: 10.1074/jbc.275.10.7013.
The interaction of the two transcriptional regulators RcsA and RcsB with a specific operator is a common mechanism in the activation of capsule biosynthesis in enteric bacteria. We describe RcsAB binding sites in the wza promoter of the operon for colanic acid biosynthesis in Escherichia coli K-12, in the galF promoter of the operon for K2 antigen biosynthesis in Klebsiella pneumoniae, and in the tviA (vipR) promoter of the operon for Vi antigen biosynthesis in Salmonella typhi. We further show the interaction of RcsAB with the rcsA promoters of various species, indicating that rcsA autoregulation also depends on the presence of both proteins. The compilation of all identified RcsAB binding sites revealed the conserved core sequence TaAGaatatTCctA, which we propose to be termed RcsAB box. The RcsAB box is also part of Bordetella pertussis BvgA binding sites and may represent a more distributed recognition motif within the LuxR superfamily of transcriptional regulators. The RcsAB box is essential for the induction of Rcs-regulated promoters. Site-specific mutations of conserved nucleotides in the RcsAB boxes of the E. coli wza and rcsA promoters resulted in an exopolysaccharide-negative phenotype and in the reduction of reporter gene expression.
两种转录调节因子RcsA和RcsB与特定操纵基因的相互作用是肠道细菌中荚膜生物合成激活的常见机制。我们描述了大肠杆菌K-12中结肠酸生物合成操纵子的wza启动子、肺炎克雷伯菌中K2抗原生物合成操纵子的galF启动子以及伤寒沙门氏菌中Vi抗原生物合成操纵子的tviA（vipR）启动子中的RcsAB结合位点。我们进一步展示了RcsAB与各种物种的rcsA启动子的相互作用，表明rcsA的自我调节也依赖于这两种蛋白质的存在。所有已鉴定的RcsAB结合位点的汇编揭示了保守的核心序列TaAGaatatTCctA，我们建议将其称为RcsAB框。RcsAB框也是百日咳博德特氏菌BvgA结合位点的一部分，可能代表转录调节因子LuxR超家族中更广泛分布的识别基序。RcsAB框对于Rcs调节的启动子的诱导至关重要。大肠杆菌wza和rcsA启动子的RcsAB框中保守核苷酸的位点特异性突变导致胞外多糖阴性表型并降低报告基因表达。
