Regulation Mechanism of the ald Gene Encoding Alanine Dehydrogenase in Mycobacterium smegmatis and Mycobacterium tuberculosis by the Lrp/AsnC Family Regulator AldR
Regulation Mechanism of the ald Gene Encoding Alanine Dehydrogenase in Mycobacterium smegmatis and Mycobacterium tuberculosis by the Lrp/AsnC Family Regulator AldR
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DOI：
10.1128/jb.00453-15
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发表时间：
2015-10-01
影响因子：
3.2
通讯作者：
Oh, Jeong-Il
中科院分区：
文献类型：
--
作者：
Jeong, Ji-A;Hyun, Jaekyung;Oh, Jeong-Il
在丙氨酸存在下，AldR 属于转录调节因子 Lrp/AsnC 家族，调节耻垢分枝杆菌中编码丙氨酸脱氢酶的 ald，其四级结构从同二聚体改变为具有开环构象的八聚体。通过 DNase I 足迹分析，在耻垢分枝杆菌 ald 基因上游鉴定出具有 GA/T-N-2-NWW/WWN-N-2-A/TC 共有序列的四个 AldR 结合位点（O2、O1、O4 和 O3）。 O2、O1 和 O4 是丙氨酸诱导 ald 表达所必需的，而 O3 直接参与 ald 表达的抑制。除了 O3 之外，由于 AldR 二聚体与 O1、O4 和 O3 的协同结合，在没有丙氨酸的情况下，O1 和 O4 也是完全抑制 ald 表达所必需的。 AldR 八聚体分子与 ald 控制区的结合被证明需要两个 AldR 结合位点，其中心之间由三个螺旋转角隔开，以及一个与两个 AldR 结合位点同相的附加结合位点。 AldR 二聚体与 DNA 的协同结合需要三个 AldR 结合位点，这些位点以三个螺旋圈的周期排列。 aldR 基因独立于丙氨酸进行负向自动调节。对耻垢分枝杆菌和结核分枝杆菌的 ald 表达进行比较分析，结合两个 ald 控制区的序列分析，我们得出结论，两种分枝杆菌中 ald 基因的表达受到相同机制的调节。 重要性 在分枝杆菌中，丙氨酸脱氢酶 (Ald) 是利用丙氨酸作为氮源和通过维持丙氨酸氧化还原状态在缺氧条件下生长所需的酶。 NADH/NAD(+) 池。据报道，ald 基因的表达受到属于 Lrp/AsnC（盛宴/饥荒）家族的 AldR 调节因子的调节，但其潜在机制尚不清楚。本研究揭示了ald在耻垢分枝杆菌和结核分枝杆菌中的调控机制。此外，本研究提出了 Lrp/AsnC（盛宴/饥荒）家族调节剂的顺式作用调节位点的广义排列模式。
In the presence of alanine, AldR, which belongs to the Lrp/AsnC family of transcriptional regulators and regulates ald encoding alanine dehydrogenase in Mycobacterium smegmatis, changes its quaternary structure from a homodimer to an octamer with an open-ring conformation. Four AldR-binding sites (O2, O1, O4, and O3) with a consensus sequence of GA/T-N-2-NWW/WWN-N-2-A/TC were identified upstream of the M. smegmatis ald gene by means of DNase I footprinting analysis. O2, O1, and O4 are required for the induction of ald expression by alanine, while O3 is directly involved in the repression of ald expression. In addition to O3, both O1 and O4 are also necessary for full repression of ald expression in the absence of alanine, due to cooperative binding of AldR dimers to O1, O4, and O3. Binding of a molecule of the AldR octamer to the ald control region was demonstrated to require two AldR-binding sites separated by three helical turns between their centers and one additional binding site that is in phase with the two AldR-binding sites. The cooperative binding of AldR dimers to DNA requires three AldR-binding sites that are aligned with a periodicity of three helical turns. The aldR gene is negatively autoregulated independently of alanine. Comparative analysis of ald expression of M. smegmatis and Mycobacterium tuberculosis in conjunction with sequence analysis of both ald control regions led us to suggest that the expression of the ald genes in both mycobacterial species is regulated by the same mechanism.IMPORTANCEIn mycobacteria, alanine dehydrogenase (Ald) is the enzyme required both to utilize alanine as a nitrogen source and to grow under hypoxic conditions by maintaining the redox state of the NADH/NAD(+) pool. Expression of the ald gene was reported to be regulated by the AldR regulator that belongs to the Lrp/AsnC (feast/famine) family, but the underlying mechanism was unknown. This study revealed the regulation mechanism of ald in Mycobacterium smegmatis and Mycobacterium tuberculosis. Furthermore, a generalized arrangement pattern of cis-acting regulatory sites for Lrp/AsnC (feast/famine) family regulators is suggested in this study.