The RcsCDB phosphorelay system controls an extremely large regulon in Enterobacteriaceae that involves processes such as biofilm formation, flagella production, synthesis of extracellular capsules and cell division. Therefore, fine-tuning of this system is essential for virulence in pathogenic microorganisms of this group. The final master effector of the RcsCDB system is the response regulator (RR) RcsB, which activates or represses multiple genes by binding to different promoter regions. This regulatory activity of RcsB can be done alone or in combination with additional transcriptional factors in phosphorylated or dephosphorylated states. The capacity of RcsB to interact with multiple promoters and partners, either dephosphorylated or phosphorylated, suggests an extremely conformational dynamism for this RR. To shed light on the activation mechanism of RcsB and its implication on promoter recognition, we solved the crystal structure of full-length RcsB from Salmonella enterica serovar Typhimurium in the presence and absence of a phosphomimetic molecule BeF₃⁻. These two novel structures have guided an extensive site-directed mutagenesis study at the structural and functional level that confirms RcsB conformational plasticity and dynamism. Our data allowed us to propose a β5-T switch mechanism where phosphorylation is coupled to alternative DNA binding ways and which highlights the conformational dynamism of RcsB to be so pleiotropic.

中文翻译：

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沙门氏菌RcsB反应调节剂中DNA相互作用的构象动力学

RcsCDB磷灰泥系统可控制肠杆菌科中的超大型调节子其中涉及诸如生物膜形成，鞭毛产生，细胞外胶囊合成和细胞分裂等过程。因此，对该系统的微调对于该组病原微生物中的毒力至关重要。RcsCDB系统的最终主要效应子是响应调节器（RR）RcsB，它通过与不同的启动子区域结合来激活或抑制多个基因。RcsB的这种调节活性可以单独完成，也可以与其他处于磷酸化或去磷酸化状态的转录因子结合使用。RcsB与多个启动子和伴侣相互作用的能力，无论是去磷酸化还是磷酸化，都表明该RR具有极强的构象活力。为了阐明RcsB的激活机制及其对启动子识别的意义，肠沙门氏菌鼠伤寒沙门氏菌在phosphomimetic分子BEF的存在和不存在₃ ^- 。这两个新颖的结构在结构和功能水平上指导了广泛的定点诱变研究，证实了RcsB的构象可塑性和活力。我们的数据使我们能够提出一种β5-T转换机制，其中磷酸化与其他DNA结合方式偶联，这突显了RcsB的构象动力学具有多效性。