Tomoyasu T, Gamer J, Bukau B, Kanemori M, Mori H, Rutman A J, Oppenheim A B, Yura T, Yamanaka K, Niki H
Department of Molecular Cell Biology, Kumamoto University School of Medicine, Japan.
EMBO J. 1995 Jun 1;14(11):2551-60. doi: 10.1002/j.1460-2075.1995.tb07253.x.
Escherichia coli FtsH is an essential integral membrane protein that has an AAA-type ATPase domain at its C-terminal cytoplasmic part, which is homologous to at least three ATPase subunits of the eukaryotic 26S proteasome. We report here that FtsH is involved in degradation of the heat-shock transcription factor sigma 32, a key element in the regulation of the E. coli heat-shock response. In the temperature-sensitive ftsH1 mutant, the amount of sigma 32 at a non-permissive temperature was higher than in the wild-type under certain conditions due to a reduced rate of degradation. In an in vitro system with purified components, FtsH catalyzed ATP-dependent degradation of biologically active histidine-tagged sigma 32. FtsH has a zinc-binding motif similar to the active site of zinc-metalloproteases. Protease activity of FtsH for histidine-tagged sigma 32 was stimulated by Zn2+ and strongly inhibited by the heavy metal chelating agent o-phenanthroline. We conclude that FtsH is a novel membrane-bound, ATP-dependent metalloprotease with activity for sigma 32. These findings indicate a new mechanism of gene regulation in E. coli.
大肠杆菌FtsH是一种必需的整合膜蛋白，在其C端胞质部分有一个AAA型ATP酶结构域，该结构域与真核生物26S蛋白酶体的至少三个ATP酶亚基同源。我们在此报告，FtsH参与热休克转录因子sigma 32的降解，sigma 32是大肠杆菌热休克反应调控中的关键元件。在温度敏感的ftsH1突变体中，在非允许温度下，由于降解速率降低，sigma 32的量在某些条件下高于野生型。在一个含有纯化成分的体外系统中，FtsH催化生物活性组氨酸标记的sigma 32的ATP依赖性降解。FtsH有一个类似于锌金属蛋白酶活性位点的锌结合基序。FtsH对组氨酸标记的sigma 32的蛋白酶活性受到Zn2+的刺激，并被重金属螯合剂邻菲罗啉强烈抑制。我们得出结论，FtsH是一种新型的膜结合、ATP依赖性金属蛋白酶，对sigma 32有活性。这些发现表明了大肠杆菌中一种新的基因调控机制。
