Khattar M M
Institute of Cell and Molecular Biology, University of Edinburgh, UK.
FEBS Lett. 1997 Sep 8;414(2):402-4. doi: 10.1016/s0014-5793(97)01024-7.
A multicopy clone was isolated which conferred resistance to the SOS inducer nitrofurantoin in an Escherichia coli lon mutant. Plasmid pHL1 was found to contain a 7-8 kbp HindIII DNA insert from a region of the chromosome at 88.5 minutes. Further characterisation of pHL1 revealed that resistance to nitrofurantoin was due to the overexpression of the hslV-hslU operon which encodes an ATP-dependent protease complex in E. coli. The overexpression of hslVU also conferred resistance to ultraviolet irradiation in the lon mutant. It is proposed that when overproduced, the HslV-HslU protease complex can degrade SulA which is an endogenous inhibitor of the essential cell division protein FtsZ. The ability of HslVU to degrade SulA in vivo suggests that Lon and HslVU may share a range of substrates. Furthermore, the suppression of lon could be used as a simple genetic test of proteolytic activity of cloned HslVU.
分离出一个多拷贝克隆，它能使大肠杆菌lon突变体对SOS诱导剂呋喃妥因产生抗性。发现质粒pHL1含有一段来自染色体88.5分钟区域的7 - 8 kbp HindIII DNA插入片段。对pHL1的进一步表征表明，对呋喃妥因的抗性是由于hslV - hslU操纵子的过表达，该操纵子在大肠杆菌中编码一种ATP依赖性蛋白酶复合体。hslVU的过表达也使lon突变体对紫外线照射产生抗性。有人提出，当过量产生时，HslV - HslU蛋白酶复合体可以降解SulA，SulA是必需细胞分裂蛋白FtsZ的内源性抑制剂。HslVU在体内降解SulA的能力表明，Lon和HslVU可能共享一系列底物。此外，lon的抑制可作为克隆的HslVU蛋白水解活性的简单遗传测试。
