Mengin-Lecreulx D, Ayala J, Bouhss A, van Heijenoort J, Parquet C, Hara H
Laboratoire des Enveloppes Bactériennes, Centre National de la Recherche Scientifique, Université Paris-Sud, 91405 Orsay Cedex, France.
J Bacteriol. 1998 Sep;180(17):4406-12. doi: 10.1128/JB.180.17.4406-4412.1998.
Recently, a promoter for the essential gene ftsI, which encodes penicillin-binding protein 3 of Escherichia coli, was precisely localized 1.9 kb upstream from this gene, at the beginning of the mra cluster of cell division and cell envelope biosynthesis genes (H. Hara, S. Yasuda, K. Horiuchi, and J. T. Park, J. Bacteriol. 179:5802-5811, 1997). Disruption of this promoter (Pmra) on the chromosome and its replacement by the lac promoter (Pmra::Plac) led to isopropyl-beta-D-thiogalactopyranoside (IPTG)-dependent cells that lysed in the absence of inducer, a defect which was complemented only when the whole region from Pmra to ftsW, the fifth gene downstream from ftsI, was provided in trans on a plasmid. In the present work, the levels of various proteins involved in peptidoglycan synthesis and cell division were precisely determined in cells in which Pmra::Plac promoter expression was repressed or fully induced. It was confirmed that the Pmra promoter is required for expression of the first nine genes of the mra cluster: mraZ (orfC), mraW (orfB), ftsL (mraR), ftsI, murE, murF, mraY, murD, and ftsW. Interestingly, three- to sixfold-decreased levels of MurG and MurC enzymes were observed in uninduced Pmra::Plac cells. This was correlated with an accumulation of the nucleotide precursors UDP-N-acetylglucosamine and UDP-N-acetylmuramic acid, substrates of these enzymes, and with a depletion of the pool of UDP-N-acetylmuramyl pentapeptide, resulting in decreased cell wall peptidoglycan synthesis. Moreover, the expression of ftsZ, the penultimate gene from this cluster, was significantly reduced when Pmra expression was repressed. It was concluded that the transcription of the genes located downstream from ftsW in the mra cluster, from murG to ftsZ, is also mainly (but not exclusively) dependent on the Pmra promoter.
最近，编码大肠杆菌青霉素结合蛋白3的必需基因ftsI的启动子被精确地定位在该基因上游1.9 kb处，位于细胞分裂和细胞包膜生物合成基因的mra簇的起始位置（原田浩、安田修、堀内健、朴哲天，《细菌学杂志》179:5802 - 5811，1997年）。染色体上该启动子（Pmra）的破坏以及用lac启动子（Pmra::Plac）对其进行替换，产生了异丙基-β-D-硫代半乳糖苷（IPTG）依赖性细胞，这些细胞在没有诱导剂的情况下会裂解，只有当从Pmra到ftsW（ftsI下游的第五个基因）的整个区域通过质粒反式提供时，该缺陷才能得到互补。在本研究中，精确测定了Pmra::Plac启动子表达被抑制或完全诱导的细胞中参与肽聚糖合成和细胞分裂的各种蛋白质的水平。证实了Pmra启动子是mra簇前九个基因表达所必需的：mraZ（orfC）、mraW（orfB）、ftsL（mraR）、ftsI、murE、murF、mraY、murD和ftsW。有趣的是，在未诱导的Pmra::Plac细胞中观察到MurG和MurC酶的水平降低了三到六倍。这与这些酶的底物核苷酸前体UDP-N-乙酰葡糖胺和UDP-N-乙酰胞壁酸的积累以及UDP-N-乙酰胞壁酰五肽库的耗尽相关，导致细胞壁肽聚糖合成减少。此外，当Pmra表达被抑制时，该簇倒数第二个基因ftsZ的表达显著降低。得出的结论是mra簇中ftsW下游从murG到ftsZ的基因转录也主要（但并非完全）依赖于Pmra启动子。
