Couñago Rafael M, Chen Nathan H, Chang Chiung-Wen, Djoko Karrera Y, McEwan Alastair G, Kobe Bostjan
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Qld 4072, Australia Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Qld 4072, Australia Institute for Molecular Bioscience, University of Queensland, Brisbane, Qld 4072, Australia
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Qld 4072, Australia Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Qld 4072, Australia.
Nucleic Acids Res. 2016 Aug 19;44(14):6981-93. doi: 10.1093/nar/gkw543. Epub 2016 Jun 15.
Pathogenic bacteria such as Haemophilus influenzae, a major cause of lower respiratory tract diseases, must cope with a range of electrophiles generated in the host or by endogenous metabolism. Formaldehyde is one such compound that can irreversibly damage proteins and DNA through alkylation and cross-linking and interfere with redox homeostasis. Its detoxification operates under the control of HiNmlR, a protein from the MerR family that lacks a specific sensor region and does not bind metal ions. We demonstrate that HiNmlR is a thiol-dependent transcription factor that modulates H. influenzae response to formaldehyde, with two cysteine residues (Cys54 and Cys71) identified to be important for its response against a formaldehyde challenge. We obtained crystal structures of HiNmlR in both the DNA-free and two DNA-bound forms, which suggest that HiNmlR enhances target gene transcription by twisting of operator DNA sequences in a two-gene operon containing overlapping promoters. Our work provides the first structural insights into the mechanism of action of MerR regulators that lack sensor regions.
诸如流感嗜血杆菌这类下呼吸道疾病的主要致病菌，必须应对宿主产生或内源性代谢产生的一系列亲电试剂。甲醛就是这样一种化合物，它可通过烷基化和交联作用不可逆地损伤蛋白质和DNA，并干扰氧化还原稳态。其解毒作用受HiNmlR调控，HiNmlR是一种来自MerR家族的蛋白质，缺乏特定的传感区域且不结合金属离子。我们证明HiNmlR是一种硫醇依赖性转录因子，可调节流感嗜血杆菌对甲醛的反应，已确定两个半胱氨酸残基（Cys54和Cys71）对其应对甲醛挑战的反应很重要。我们获得了无DNA形式和两种DNA结合形式的HiNmlR晶体结构，这表明HiNmlR通过在含有重叠启动子的双基因操纵子中扭曲操纵子DNA序列来增强靶基因转录。我们的工作首次提供了对缺乏传感区域的MerR调节因子作用机制的结构见解。
