Abstact

HpaR is a transcriptional regulator belonging to the MarR family, which modulates bacterial virulence. Here, we report the biochemical and structural characterization of HpaR in Xanthomonas campestris pv. campestris (XcHpaR) and build a complex between HpaR and DNA. Our study revealed that XcHpaR can bind upstream of the divergently transcribed hrpX and hrpG genes and activate their transcription in vitro. Structural analysis of the XcHpaR dimer indicates that the monomer possesses an additional extended N-terminal alpha-helix (alpha0). Additionally, structural comparison uncovers that a winged-loop conformational change in the DNA-binding domain is essential for XcHpaR activation. Moreover, five key residues (K37, S53, K83, R89, R110) participate in DNA recognition, with R110 being highly conserved within the MarR family. This study provides valuable insights about the DNA recognition of XcHpaR and expands our understanding of the regulatory role of HpaR.