Structural Insights Into the Transcriptional Regulation of HigBA Toxin–Antitoxin System by Antitoxin HigA in Pseudomonas aeruginosa
Structural Insights Into the Transcriptional Regulation of HigBA Toxin–Antitoxin System by Antitoxin HigA in Pseudomonas aeruginosa
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DOI：
10.3389/fmicb.2019.03158
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发表时间：
2020-01
影响因子：
5.2
通讯作者：
Y. Liu;Zengqiang Gao;Guangfeng Liu;Zhi Geng;Yuhui Dong;Heng Zhang
中科院分区：
文献类型：
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作者：
Y. Liu;Zengqiang Gao;Guangfeng Liu;Zhi Geng;Yuhui Dong;Heng Zhang
HigA -HigA是一种细菌毒素-抗毒素（TA）系统，其中抗毒素HigA可以掩盖毒素HigB的核糖核酸内酶活性，并通过结合其自身启动子区域抑制TA操纵子的转录。条件致病菌铜绿假单胞菌HigBA （PaHigBA）通过减少多种毒力因子的产生和生物膜的形成与致病性密切相关。然而，PaHigA转录HigBA TA操纵子的分子机制尚不清楚。在这里，我们报道了PaHigA结合higBA操纵子启动子区域的晶体结构，其中包含两个相同的回文序列，分辨率为3.14 Å。启动子DNA由两个合作二聚体结合，基本上环绕完整的回文区。来自两种二聚体的螺旋-转-螺旋（HTH）基序插入DNA相对两侧的主要凹槽中。DNA采用标准的B-DNA构象，蛋白质和DNA之间的所有氢键都是由DNA磷酸主链介导的。PaHigA- dna复合物的高分辨率结构在2.50 Å进一步揭示了三个水分子桥接dna结合界面，并介导回文序列碱基与PaHigA （Thr40， Asp43和Arg49）之间的相互作用。基于结构的诱变证实了这些残基对PaHigA的特异性dna结合能力至关重要。因此，我们的结构-功能研究阐明了二聚体-二聚体的协同转录抑制机制，并可能有助于了解PaHigA对铜绿假单胞菌多种毒力因子的调控。
HigB-HigA is a bacterial toxin–antitoxin (TA) system in which the antitoxin HigA can mask the endoribonuclease activity of toxin HigB and repress the transcription of the TA operon by binding to its own promoter region. The opportunistic pathogen Pseudomonas aeruginosa HigBA (PaHigBA) is closely associated with the pathogenicity by reducing the production of multiple virulence factors and biofilm formation. However, the molecular mechanism underlying HigBA TA operon transcription by PaHigA remains elusive. Here, we report the crystal structure of PaHigA binding to the promoter region of higBA operon containing two identical palindromic sequences at 3.14 Å resolution. The promoter DNA is bound by two cooperative dimers to essentially encircle the intact palindrome region. The helix-turn-helix (HTH) motifs from the two dimers insert into the major grooves of the DNA at the opposite sides. The DNA adopts a canonical B-DNA conformation and all the hydrogen bonds between protein and DNA are mediated by the DNA phosphate backbone. A higher resolution structure of PaHigA-DNA complex at 2.50 Å further revealed three water molecules bridged the DNA-binding interface and mediated the interactions between the bases of palindromic sequences and PaHigA (Thr40, Asp43, and Arg49). Structure-based mutagenesis confirmed these residues are essential for the specific DNA-binding ability of PaHigA. Our structure–function studies therefore elucidated the cooperative dimer–dimer transcription repression mechanism, and may help to understand the regulation of multiple virulence factors by PaHigA in P. aeruginosa.