Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany.
J Bacteriol. 2011 Mar;193(5):1237-49. doi: 10.1128/JB.01032-10. Epub 2010 Dec 23.
The two-component signal transduction system consisting of the sensor kinase MtrB and the response regulator MtrA is highly conserved in corynebacteria and mycobacteria. Whereas mtrA of Mycobacterium tuberculosis was reported to be essential, we recently succeeded in creating ΔmtrAB and ΔmtrA deletion mutants of Corynebacterium glutamicum and provided evidence that mepA and nlpC, both encoding putative cell wall peptidases, are directly repressed by MtrA, whereas proP and betP, both encoding carriers for compatible solutes, are directly activated by MtrA. In the present study, novel MtrA target genes were identified, including mepB, encoding another putative cell wall peptidase. The repressor or activator functions of MtrA correlate with the distance between the MtrA binding site and the transcriptional start site. From the identified binding sites within 20 target promoters, a 19-bp MtrA consensus motif was derived which represents a direct repeat of 8 base pairs separated by 3 base pairs. Gene expression of a strain containing MtrA with a D53N mutation instead of wild-type MtrA resembled that of a ΔmtrA mutant, indicating that MtrA is active in its phosphorylated form. This result was confirmed by electrophoretic mobility shift assays with phosphorylated MtrA which showed an increased binding affinity.
由传感器激酶 MtrB 和响应调节器 MtrA 组成的双组分信号转导系统在棒状杆菌和分枝杆菌中高度保守。虽然分枝杆菌结核 MtrA 被报道为必需的，但我们最近成功地创建了谷氨酸棒状杆菌的ΔmtrAB 和ΔmtrA 缺失突变体，并提供了证据表明，编码假定细胞壁肽酶的 mepA 和 nlpC 直接受到 MtrA 的抑制，而编码相容溶质载体的 proP 和 betP 直接被 MtrA 激活。在本研究中，鉴定了新的 MtrA 靶基因，包括编码另一种假定细胞壁肽酶的 mepB。MtrA 的阻遏或激活功能与 MtrA 结合位点与转录起始位点之间的距离相关。从 20 个靶启动子中的鉴定结合位点中，衍生出了一个 19 个碱基对的 MtrA 共有基序，它代表了由 3 个碱基对分隔的 8 个碱基对的直接重复。含有 D53N 突变而非野生型 MtrA 的 MtrA 的菌株的基因表达类似于ΔmtrA 突变体，表明 MtrA 以其磷酸化形式发挥作用。这一结果通过磷酸化 MtrA 的电泳迁移率变动分析得到了证实，该分析显示出增加的结合亲和力。
