Bardwell J C, McGovern K, Beckwith J
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Cell. 1991 Nov 1;67(3):581-9. doi: 10.1016/0092-8674(91)90532-4.
We describe a mutation (dsbA) that renders Escherichia coli severely defective in disulfide bond formation. In dsbA mutant cells, pulse-labeled beta-lactamase, alkaline phosphatase, and OmpA are secreted but largely lack disulfide bonds. These disulfideless proteins may represent in vivo folding intermediates, since they are protease sensitive and chase slowly into stable oxidized forms. The dsbA gene codes for a 21,000 Mr periplasmic protein containing the sequence cys-pro-his-cys, which resembles the active sites of certain disulfide oxidoreductases. The purified DsbA protein is capable of reducing the disulfide bonds of insulin, an activity that it shares with these disulfide oxidoreductases. Our results suggest that disulfide bond formation is facilitated by DsbA in vivo.
我们描述了一种突变（dsbA），该突变使大肠杆菌在二硫键形成方面存在严重缺陷。在dsbA突变细胞中，经脉冲标记的β-内酰胺酶、碱性磷酸酶和外膜蛋白A被分泌出来，但大部分缺乏二硫键。这些无二硫键的蛋白质可能代表体内折叠中间体，因为它们对蛋白酶敏感，并且缓慢转化为稳定的氧化形式。dsbA基因编码一种21,000道尔顿的周质蛋白，其含有半胱氨酸-脯氨酸-组氨酸-半胱氨酸序列，这类似于某些二硫键氧化还原酶的活性位点。纯化的DsbA蛋白能够还原胰岛素的二硫键，这是它与这些二硫键氧化还原酶共有的一种活性。我们的结果表明，DsbA在体内促进了二硫键的形成。
