Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia, USA.
Mol Microbiol. 2024 Jun;121(6):1228-1244. doi: 10.1111/mmi.15278. Epub 2024 May 12.
Bacteria contain conserved mechanisms to control the intracellular levels of metal ions. Metalloregulatory transcription factors bind metal cations and play a central role in regulating gene expression of metal transporters. Often, these transcription factors regulate transcription by binding to a specific DNA sequence in the promoter region of target genes. Understanding the preferred DNA-binding sequence for transcriptional regulators can help uncover novel gene targets and provide insight into the biological role of the transcription factor in the host organism. Here, we identify consensus DNA-binding sequences and subsequent transcription regulatory networks for two metalloregulators from the ferric uptake regulator (FUR) and diphtheria toxin repressor (DtxR) superfamilies in Thermus thermophilus HB8. By homology search, we classify the DtxR homolog as a manganese-specific, MntR (TtMntR), and the FUR homolog as a peroxide-sensing, PerR (TtPerR). Both transcription factors repress separate ZIP transporter genes in vivo, and TtPerR acts as a bifunctional transcription regulator by activating the expression of ferric and hemin transport systems. We show TtPerR and TtMntR bind DNA in the presence of manganese in vitro and in vivo; however, TtPerR is unable to bind DNA in the presence of iron, likely due to iron-mediated histidine oxidation. Unlike canonical PerR homologs, TtPerR does not appear to contribute to peroxide detoxification. Instead, the TtPerR regulon and DNA binding sequence are more reminiscent of Fur or Mur homologs. Collectively, these results highlight the similarities and differences between two metalloregulatory superfamilies and underscore the interplay of manganese and iron in transcription factor regulation.
细菌中存在保守的机制来控制金属离子的细胞内水平。金属调控转录因子结合金属阳离子，在调控金属转运蛋白的基因表达中发挥核心作用。通常，这些转录因子通过结合靶基因启动子区域中的特定 DNA 序列来调节转录。了解转录调控因子的首选 DNA 结合序列有助于发现新的基因靶标，并深入了解转录因子在宿主生物中的生物学作用。在这里，我们确定了耐热栖热菌中来自铁摄取调控因子 (FUR) 和白喉毒素阻遏物 (DtxR) 超家族的两种金属调控因子的保守 DNA 结合序列和随后的转录调控网络。通过同源搜索，我们将 DtxR 同源物归类为锰特异性的 MntR（TtMntR），而 FUR 同源物归类为过氧化物感应的 PerR（TtPerR）。这两种转录因子在体内都抑制不同的 ZIP 转运体基因，而 TtPerR 作为双功能转录调控因子，通过激活铁和血红素转运系统的表达来发挥作用。我们表明 TtPerR 和 TtMntR 在体内外锰存在的情况下结合 DNA；然而，TtPerR 无法在铁存在的情况下结合 DNA，这可能是由于铁介导的组氨酸氧化。与典型的 PerR 同源物不同，TtPerR 似乎不参与过氧化物解毒。相反，TtPerR 调控子和 DNA 结合序列更类似于 Fur 或 Mur 同源物。总之，这些结果突出了两种金属调控超家族之间的相似性和差异性，并强调了锰和铁在转录因子调节中的相互作用。
