文献类型：期刊文献

英文题名：The Nitrogen Regulator GlnR Directly Controls Transcription of the prpDBC Operon Involved in Methylcitrate Cycle in Mycobacterium smegmatis

作者：Liu, Wei-Bing[1];Liu, Xin-Xin[1];Shen, Meng-Jia[1];She, Guo-Lan[2];Ye, Bang-Ce[1,2]

机构：[1]East China Univ Sci & Technol, State Key Lab Bioreactor Engn, Biomed Nanotechnol Ctr, Lab Biosyst & Microanal, Shanghai, Peoples R China;[2]Zhejiang Univ Technol, Coll Pharmaceut Sci, Collaborat Innovat Ctr Yangtze River Delta Reg Gr, Hangzhou, Zhejiang, Peoples R China

年份：2019

卷号：201

期号：8

外文期刊名：JOURNAL OF BACTERIOLOGY

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000462322300006)】；

基金：This work was supported by grants from the National Natural Science Foundation of China (31730004, 21335003, and 21575089) and supported by the Open Funding Project of the State Key Laboratory of Bioreactor Engineering.

语种：英文

外文关键词：Mycobacterium smegmatis; nitrogen regulator GlnR; methylcitrate cycle; prpDBC operon

摘要：Mycobacterium tuberculosis utilizes fatty acids of the host as the carbon source. Metabolism of odd-chain fatty acids by Mycobacterium tuberculosis produces propionyl coenzyme A (propionyl-CoA). The methylcitrate cycle is essential for mycobacteria to utilize the propionyl-CoA to persist and grow on these fatty acids. In M. smegmatis, methylcitrate synthase, methylcitrate dehydratase, and methylisocitrate lyase involved in the methylcitrate cycle are encoded by prpC, prpD, and prpB, respectively, in operon prpDBC. In this study, we found that the nitrogen regulator GlnR directly binds to the promoter region of the prpDBC operon and inhibits its transcription. The binding motif of GlnR was identified by bioinformatic analysis and validated using DNase I footprinting and electrophoretic mobility shift assays. The GlnR-binding motif is separated by a 164-bp sequence from the binding site of PrpR, a pathway-specific transcriptional activator of methylcitrate cycle, but the binding affinity of GlnR to prpDBC is much stronger than that of PrpR. Deletion of glnii resulted in faster growth in propionate or cholesterol medium compared with the wild-type strain. The Delta glnR mutant strain also showed a higher survival rate in macrophages. These results illustrated that the nitrogen regulator GlnR regulates the methylcitrate cycle through direct repression of the transcription of the prpDBC operon. This finding not only suggests an unprecedented link between nitrogen metabolism and the methylcitrate pathway but also reveals a potential target for controlling the growth of pathogenic mycobacteria. IMPORTANCE The success of mycobacteria survival in macrophage depends on its ability to assimilate fatty acids and cholesterol from the host. The cholesterol and fatty acids are catabolized via a-oxidation to generate propionyl coenzyme A (propionyl-CoA), which is then primarily metabolized via the methylcitrate cycle. Here, we found a typical GlnR binding box in the prp operon, and the affinity is much stronger than that of PrpR, a transcriptional activator of methylcitrate cycle. Furthermore, GlnR repressed the transcription of the prp operon. Deletion of glnR significantly enhanced the growth of Mycobacterium tuberculosis in propionate or cholesterol medium, as well as viability in macrophages. These findings provide new insights into the regulatory mechanisms underlying the cross talk of nitrogen and carbon metabolisms in mycobacteria.