Yousuf Suhail, Angara Rajendra Kumar, Roy Ajit, Gupta Shailesh Kumar, Misra Rohan, Ranjan Akash
1Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, 500039, India.
2Graduate studies, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India.
Microbiology (Reading). 2018 Sep;164(9):1133-1145. doi: 10.1099/mic.0.000686. Epub 2018 Jul 11.
Lipid metabolism is critical to Mycobacterium tuberculosis survival and infection. Unlike Escherichia coli, which has a single FadR, the M. tuberculosis genome encodes five proteins of the FadR sub-family. While the role of E. coli FadR as a regulator of fatty acid metabolism is well known, the definitive functions of M. tuberculosis FadR proteins are still under investigation. An interesting question about the M. tuberculosis FadRs remains open: which one of these proteins is the functional homologue of E. coli FadR? To address this, we have applied two different approaches. The first one was the bioinformatics approach and the second one was the classical molecular genetic approach involving complementation studies. Surprisingly, the results of these two approaches did not agree. Among the five M. tuberculosis FadRs, Rv0494 shared the highest sequence similarity with FadR and Rv0586 was the second best match. However, only Rv0586, but not Rv0494, could complement E. coli ∆fadR, indicating that Rv0586 is the M. tuberculosis functional homologue of FadR. Further studies showed that both regulators, Rv0494 and Rv0586, show similar responsiveness to LCFA, and have conserved critical residues for DNA binding. However, analysis of the operator site indicated that the inter-palindromic distance required for DNA binding differs for the two regulators. The differences in the binding site selection helped in the success of Rv0586 binding to fadB upstream over Rv0494 and may have played a critical role in complementing E. coli ∆fadR. Further, for the first time, we report the lipid-responsive nature of Rv0586.
脂质代谢对结核分枝杆菌的存活和感染至关重要。与只有单一FadR的大肠杆菌不同，结核分枝杆菌基因组编码了五个FadR亚家族蛋白。虽然大肠杆菌FadR作为脂肪酸代谢调节因子的作用已为人所知，但结核分枝杆菌FadR蛋白的确切功能仍在研究中。关于结核分枝杆菌FadR的一个有趣问题仍然悬而未决：这些蛋白中哪一个是大肠杆菌FadR的功能同源物？为了解决这个问题，我们应用了两种不同的方法。第一种是生物信息学方法，第二种是涉及互补研究的经典分子遗传学方法。令人惊讶的是，这两种方法的结果并不一致。在五个结核分枝杆菌FadR中，Rv0494与FadR的序列相似性最高，Rv0586是第二匹配的。然而，只有Rv0586，而不是Rv0494，能够互补大肠杆菌∆fadR，这表明Rv0586是结核分枝杆菌中FadR的功能同源物。进一步的研究表明，Rv0494和Rv0586这两个调节因子对长链脂肪酸（LCFA）表现出相似的反应性，并且具有保守的DNA结合关键残基。然而，对操纵子位点的分析表明，这两个调节因子DNA结合所需的回文间距离不同。结合位点选择的差异有助于Rv0586比Rv0494更成功地结合到fadB上游，并且可能在互补大肠杆菌∆fadR中起关键作用。此外，我们首次报道了Rv0586的脂质反应特性。
