Bertani D, Oppenheim A B, Narberhaus F
Institut fur Mikrobiologie, ETH-Zentrum, Zürich, Switzerland.
FEBS Lett. 2001 Mar 23;493(1):17-20. doi: 10.1016/s0014-5793(01)02266-9.
The proteolysis of regulatory proteins plays an important role in the control of gene expression. The Escherichia coli heat shock sigma factor RpoH (sigma(32)) is highly unstable. Its instability is determined by interactions with the DnaK chaperone machine, RNA polymerase and the ATP-dependent protease FtsH. Bradyrhizobium japonicum expresses three RpoH proteins of which RpoH(1) is highly stable. To determine which regions of E. coli RpoH determine protein lability, we generated a number of truncated versions and hybrid proteins. Truncation of N-terminal amino acids had no, and deletion of C-terminal amino acids only a minor effect on stability of RpoH. A major determinant of RpoH lability was mapped to a region of about 85 amino acids (residues 36-122) roughly comprising the sigma factor region 2. This is the first demonstration of an internal RpoH region being responsible for FtsH-mediated degradation.
调节蛋白的蛋白水解在基因表达调控中起着重要作用。大肠杆菌热休克σ因子RpoH（σ32）高度不稳定。其不稳定性由与DnaK伴侣机器、RNA聚合酶和ATP依赖性蛋白酶FtsH的相互作用决定。日本慢生根瘤菌表达三种RpoH蛋白，其中RpoH(1)高度稳定。为了确定大肠杆菌RpoH的哪些区域决定蛋白质的不稳定性，我们生成了许多截短版本和杂交蛋白。N端氨基酸的截短对RpoH的稳定性没有影响，而C端氨基酸的缺失对其稳定性只有轻微影响。RpoH不稳定性的一个主要决定因素被定位到大约85个氨基酸（第36-122位氨基酸残基）的区域，该区域大致包含σ因子的2区。这是首次证明RpoH内部区域负责FtsH介导的降解。
