Skorko-Glonek Joanna, Sobiecka-Szkatula Anna, Narkiewicz Joanna, Lipinska Barbara
University of Gdansk, Department of Biochemistry, Kładki 24, 80-822 Gdansk, Poland.
Microbiology (Reading). 2008 Dec;154(Pt 12):3649-3658. doi: 10.1099/mic.0.2008/020487-0.
The HtrA (DegP) protein from Escherichia coli is a periplasmic protease whose function is to protect cells from the deleterious effects of various stress conditions. At temperatures below 28 degrees C the proteolytic activity of HtrA was regarded as negligible and it was believed that the protein mainly plays the role of a chaperone. In the present work we provide evidence that HtrA can in fact act as a protease at low temperatures. Under folding stress, caused by disturbances in the disulfide bond formation, the lack of proteolytic activity of HtrA lowered the survival rates of mutant strains deprived of a functional DsbA/DsbB oxidoreductase system. HtrA degraded efficiently the unfolded, reduced alkaline phosphatase at 20 degrees C, both in vivo and in vitro. The cleavage was most efficient in the case of HtrA deprived of its internal S-S bond; therefore we expect that the reduction of HtrA may play a regulatory role in proteolysis.
来自大肠杆菌的HtrA（DegP）蛋白是一种周质蛋白酶，其功能是保护细胞免受各种应激条件的有害影响。在低于28摄氏度的温度下，HtrA的蛋白水解活性被认为可忽略不计，并且人们认为该蛋白主要起伴侣蛋白的作用。在本研究中，我们提供证据表明，HtrA实际上在低温下可作为一种蛋白酶发挥作用。在由二硫键形成紊乱引起的折叠应激下，HtrA蛋白水解活性的缺乏降低了缺乏功能性DsbA/DsbB氧化还原酶系统的突变菌株的存活率。在体内和体外，HtrA在20摄氏度时都能有效降解未折叠的、还原型碱性磷酸酶。对于缺失内部二硫键的HtrA，这种切割最为有效；因此我们预计HtrA的还原可能在蛋白水解中起调节作用。
