School of Pharmacy and Life Sciences, Jiujiang University, Jiujiang, 332000, PR China.
School of Pharmacy and Life Sciences, Jiujiang University, Jiujiang, 332000, PR China.
Biochimie. 2019 Dec;167:34-41. doi: 10.1016/j.biochi.2019.08.018. Epub 2019 Sep 3.
ArgR, a transcriptional regulator belonging to the AraC/XylS family, plays a key role in arginine metabolism regulation. ArgR has also been found to repress the transcription of a lipase gene, but its molecular mechanism is still unknown. In this study, we investigated the molecular mechanism acting on the expression of intracellular lipase gene lipA regulated by ArgR in Pseudomonas protegens Pf-5 through knockout and overexpression of argR, detection of DNA-protein interaction in vivo, determining whole-cell lipase activities of various strains derived from Pf-5, and examining β-galactosidase activities of various lacZ fusions. The results demonstrated that ArgR inhibits lipA expression at the transcriptional level. Further results showed that the inhibition of lipA transcription by ArgR is mediated by binding to the ArgR binding site of lipA promoter to produce steric hindrance, in which the common sequence, TGTCGC is crucial for the ArgR binding. Besides, arginine inhibits lipA expression in both wild-type and argR mutant, and shows a synergistic inhibition on lipA expression when combined with ArgR. To the best of our knowledge, this is the first report on ArgR directly repressing the transcription of a lipase gene.
ArgR 是一种转录调控因子，属于 AraC/XylS 家族，在精氨酸代谢调控中起着关键作用。ArgR 也被发现可以抑制脂肪酶基因 lipA 的转录，但它的分子机制尚不清楚。在本研究中，我们通过敲除和过表达 argR 来研究 Pseudomonas protegens Pf-5 中 ArgR 对细胞内脂肪酶基因 lipA 表达的作用机制，通过体内检测 DNA-蛋白相互作用，确定源自 Pf-5 的各种菌株的全细胞脂肪酶活性，并检查各种 lacZ 融合物的β-半乳糖苷酶活性。结果表明，ArgR 在转录水平上抑制 lipA 的表达。进一步的结果表明，ArgR 通过结合 lipA 启动子的 ArgR 结合位点来抑制 lipA 转录，从而产生空间位阻，其中共同序列 TGTCGC 对 ArgR 结合至关重要。此外，精氨酸在野生型和 argR 突变体中均抑制 lipA 的表达，并且与 ArgR 结合时对 lipA 的表达表现出协同抑制作用。据我们所知，这是首次报道 ArgR 直接抑制脂肪酶基因的转录。
