Post-translational modifications such as phosphorylation, nitrosylation, and pupylation modulate multiple cellular processes in Mycobacterium tuberculosis. While protein methylation at lysine and arginine residues is widespread in eukaryotes, to date only two methylated proteins in Mtb have been identified. Here, we report the identification of methylation at lysine and/or arginine residues in nine mycobacterial proteins. Among the proteins identified, we chose MtrA, an essential response regulator of a two-component signaling system, which gets methylated on multiple lysine and arginine residues to examine the functional consequences of methylation. While methylation of K207 confers a marginal decrease in the DNA-binding ability of MtrA, methylation of R122 or K204 significantly reduces the interaction with the DNA. Overexpression of S-adenosyl homocysteine hydrolase (SahH), an enzyme that modulates the levels of S-adenosyl methionine in mycobacteria decreases the extent of MtrA methylation. Most importantly, we show that decreased MtrA methylation results in transcriptional activation of mtrA and sahH promoters. Collectively, we identify novel methylated proteins, expand the list of modifications in mycobacteria by adding arginine methylation, and show that methylation regulates MtrA activity. We propose that protein methylation could be a more prevalent modification in mycobacterial proteins.

中文翻译：

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分枝杆菌中两组分应答调节剂MtrA的甲基化负调节其DNA结合和转录激活

翻译后修饰（例如磷酸化，亚硝基化和pupylation）可调节结核分枝杆菌中的多个细胞过程。虽然在真核生物中赖氨酸和精氨酸残基的蛋白质甲基化很普遍，但迄今为止，仅在Mtb中鉴定出两种甲基化蛋白质。在这里，我们报告了九种分枝杆菌蛋白中赖氨酸和/或精氨酸残基甲基化的鉴定。在鉴定出的蛋白质中，我们选择了MtrA，它是两组分信号系统的重要应答调节剂，它在多个赖氨酸和精氨酸残基上被甲基化，以检查甲基化的功能后果。尽管K207的甲基化使MtrA的DNA结合能力略有下降，但R122或K204的甲基化却大大降低了与DNA的相互作用。S-腺苷高半胱氨酸水解酶（SahH​​）的过表达，一种可调节分枝杆菌中S-腺苷甲硫氨酸水平的酶，可降低MtrA甲基化的程度。最重要的是，我们表明降低的MtrA甲基化会导致mtrA和sahH启动子的转录激活。总的来说，我们确定了新型的甲基化蛋白，通过添加精氨酸甲基化扩大了分枝杆菌的修饰范围，并表明甲基化调节了MtrA活性。我们建议蛋白质甲基化可能是在分枝杆菌蛋白质中更普遍的修饰。我们表明减少的MtrA甲基化导致mtrA和sahH启动子的转录激活。总的来说，我们确定了新型的甲基化蛋白，通过添加精氨酸甲基化扩大了分枝杆菌的修饰范围，并表明甲基化调节了MtrA活性。我们建议蛋白质甲基化可能是在分枝杆菌蛋白质中更普遍的修饰。我们表明减少的MtrA甲基化导致mtrA和sahH启动子的转录激活。总的来说，我们确定了新型的甲基化蛋白，通过添加精氨酸甲基化扩大了分枝杆菌的修饰范围，并表明甲基化调节了MtrA活性。我们建议蛋白质甲基化可能是在分枝杆菌蛋白质中更普遍的修饰。