大肠杆菌二硫键形成相关蛋白的结构、功能及其在基因工程表达外源蛋白上的应用

大肠杆菌分泌蛋白二硫键的形成是一系列蛋白协同作用的结果，主要是Dsb家族蛋白，迄今为止共发现了DsbA、DsbB、DsbC、DsbD、DsbE和DsbG。在体内，DsbA负责氧化两个巯基形成二硫键，DsbB则负责DsbA的再氧化。DsbC和DsbG负责校正DsbA导入的异常二硫键，DsbD则负责对DsbC和DsbG进行再还原，DsbE的功能与DsbD类似。除了直接和二硫键的形成相关外，DsbA、DsbC和DsbG都有分子伴侣功能。它们的分子伴侣功能独立于二硫键形成酶的活性并且对二硫键形成酶活性具有明显的促进作用。基于Dsb蛋白的功能特性，利用它们以大肠杆菌为宿主表达外源蛋白，特别是含有二硫键的蛋白，取得了很多成功的例子。本文简要介绍了这方面的进展，显示Dsb蛋白在促进外源蛋白在大肠杆菌中以可溶形式表达方面具有广阔的应用前景。

Escherichia coli Disulfide-forming Related Proteins:Structures, Functions and Their Application in Gene Engineering for Expressing Heterologous Proteins in Escherichia coli

The formation of disulfide bonds in secreted proteins of E. coli is a synergetic process depending on a series of Dsb proteins containing DsbA, DsbB, DsbC, DsbD, DsbE and DsbG. DsbA functions as an oxidant to form a disulfide bond between two -SH- in vivo and DsbB reactivates DsbA by reoxidizing it. Both DsbC and DsbG, two periplasmic proteins with isomerase activity, can correct mis-paired disulfide bonds introduced by DsbA although they recognize different substrates. DsbD, an inner membrane protein, plays a role in reducing DsbC and DsbG in vivo. It is regarded that DsbE has the similar function with DsbD. All DsbA, DsbC and DsbG have chaperone activity besides involving in the formation of disulfide bonds. Furthermore, their chaperone activity can promote the formation of protein disulfide bonds.There are a few reports dealing with soluble expression of heterologous proteins containing disulfide bonds assisted by DsbA and DsbC in E. coli. So far there has been no reports about the soluble expression of heterologous proteins promoted by DsbG. Our experiments first demonstrated that both DsbC and DsbG can improve the expression of single chain antibodies as soluble and functional forms in E. coli, and DsbG has additive effects with DsbC.