Shanghai Center for Systems Biomedicine, Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, 200240, China.
National Key Laboratory of Biomacromolecules, Key Laboratory of Non-Coding RNA and Key Laboratory of Protein and Peptide Pharmaceuticals, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
Sci Rep. 2017 Jul 19;7(1):5860. doi: 10.1038/s41598-017-06289-7.
Tuberculosis is still on the top of infectious diseases list on both mobility and mortality, especially due to drug-resistance of Mycobacterium tuberculosis (M.tb). Ethionamide (ETH) is one of effective second line anti-TB drugs, a synthetic compound similar to isoniazid (INH) structurally, with existing severe problem of ETH resistance. ETH is a prodrug, which is activated by Etha inside M.tb, and etha is transcriptionally repressed by Ethr. We found that c-di-GMP could bind Ethr, enhanced the binding of Ethr to the promoter of etha, and then repressed the transcription of etha, thus caused resistance of M.tb to ETH. Through docking analysis and in vitro validation, we identified that c-di-GMP binds 3 amino acids of Ethr, i.e., Q125, R181 and E190, while the first 2 were the major binding sites. Homology analysis showed that Ethr was highly conservative among mycobacteria. Further docking analysis showed that c-di-GMP preferentially bound proteins of TetR family at the junction hole of symmetric dimer or tetramer proteins. Our results suggest a possible drug-resistance mechanism of ETH through the regulation of Ethr by c-di-GMP.
结核病在传染病的发病率和死亡率方面仍然位居榜首，尤其是由于结核分枝杆菌（M.tb）的耐药性。乙硫异烟胺（ETH）是一种有效的二线抗结核药物，是一种结构上类似于异烟肼（INH）的合成化合物，目前存在严重的 ETH 耐药问题。ETH 是一种前体药物，在 M.tb 中被 Etha 激活，而 Ethr 转录抑制 Etha。我们发现 c-di-GMP 可以结合 Ethr，增强 Ethr 与 etha 启动子的结合，从而抑制 etha 的转录，从而导致 M.tb 对 ETH 的耐药性。通过对接分析和体外验证，我们确定 c-di-GMP 结合 Ethr 的 3 个氨基酸，即 Q125、R181 和 E190，而前 2 个是主要结合位点。同源性分析表明，Ethr 在分枝杆菌中高度保守。进一步的对接分析表明，c-di-GMP 优先结合 TetR 家族蛋白在对称二聚体或四聚体蛋白的连接孔处。我们的结果表明，c-di-GMP 通过调节 Ethr 可能是 ETH 耐药的一种机制。
