大肠杆菌二硫键形成蛋白A(DsbA)研究进展

Study on Disulfide Bond Formation Protein A in Escherichia coli

二硫键形成蛋白A(DisulfidebondformationproteinA,DsbA)是存在于大肠杆菌周质胞腔内的一种参与新生蛋白质折叠过程中催化二硫键形成的折叠酶。综述了DsbA三维结构、进化过程、协助蛋白质体内外复性方面的研究进展。DsbA比硫氧还原蛋白具有更强的氧化性,其强氧化性来自于Cys30残基异常低的pKa值和不稳定的氧化型结构,通过定点突变的研究表明了Cys30残基是DsbA活性中心最关键的氨基酸残基之一。DsbA不论在体内与目标蛋白融合表达还是在体外以折叠酶形式添加,都能有效地催化蛋白质的折叠复性,同时DsbA还具有部分分子伴侣的活性。

Disulfide bond formation protein A, DsbA, is one of the important proteins located in E. coli periplasm, which is a foldase facilitating the folding of nascent secreted proteins, especially for those with many pairs of disulfide bonds. The crystal structure and phylogenetic analysis of DsbA and DsbA-mediated protein folding, alternatively in vivo and in vitro, are summarized. Both the extremely low pKa of Cys^30, about 3.5, and the destabilizing effect of the active site disulfide contribute to its strong oxidizing power. The Cys^30 is also considered as the most important residue closely related to its activity using site-directed mutagenesis methodology. DsbA could effectively assist proteins folding, both in vivo coexpressed with the target protein, and in vitro replenished as foldases. Moreover, DsbA also has the chaperone-like activity in the assistant refolding of genetically engineered inclusion bodies.