The BvgAS two-component system regulates virulence gene expression in Bordetella pertussis. Although precise three-dimensional structural information is not available for the response regulator BvgA, its sequence conservation with E. coli NarL and previous studies have indicated that it is composed of 3 domains: an N-terminal domain (NTD) containing the phosphorylation site, a linker, and a DNA-binding C-terminal domain (CTD). Previous work has determined how BvgA^CTD dimers interact with the promoter (P_fhaB) of fhaB, the gene encoding the virulence adhesin filamentous hemagglutinin. Here we use molecular modeling, FeBABE footprinting, and crosslinking to show that within the transcription complex of phosphorylated BvgA (BvgA∼P), B. pertussis RNAP, and P_fhaB, the NTDs displace from the CTDs and are positioned at specific locations relative to the three BvgA∼P binding sites. Our work identifies a patch of the NTD that faces the DNA and suggests that BvgA∼P undergoes a conformational rearrangement that relocates the NTD to allow productive interaction of the CTD with the DNA.

BvgAS 双组分系统调节百日咳博德特氏菌的毒力基因表达。尽管响应调节因子 BvgA 无法获得精确的三维结构信息，但其与大肠杆菌NarL 的序列保守性和先前的研究表明它由 3 个结构域组成：包含磷酸化位点的 N 末端结构域 (NTD)，一个接头和一个 DNA 结合的 C 末端结构域 (CTD)。以前的工作已经确定了 BvgA ^CTD二聚体如何与 fhaB 的启动子 (P _fhaB )相互作用，编码毒力粘附素丝状血凝素的基因。在这里，我们使用分子建模、FeBABE 足迹和交联来显示在磷酸化 BvgA (BvgA∼P)、B. pertussis RNAP 和 P _fhaB的转录复合物中， NTD 从 CTD 取代并定位在相对于三个 BvgA∼P 结合位点。我们的工作确定了一块面向 DNA 的 NTD，并表明 BvgA∼P 经历了构象重排，重新定位 NTD 以允许 CTD 与 DNA 进行有效的相互作用。