Studier F W
Biology Department, Brookhaven National Laboratory Upton, NY 11973.
J Mol Biol. 1991 May 5;219(1):37-44. doi: 10.1016/0022-2836(91)90855-z.
Bacteriophage T7 lysozyme, a natural inhibitor of T7 RNA polymerase, can reduce basal activity from an inducible gene for T7 RNA polymerase and allow relatively toxic genes to be established in the same cell under control of a T7 promoter. Low levels of T7 lysozyme supplied by plasmids pLysS or pLysL, which are compatible with the pET vectors for expressing genes from a T7 promoter, are sufficient to stabilize many target plasmids and yet allow high levels of target protein to be produced upon induction of T7 RNA polymerase. Higher levels of lysozyme supplied by plasmids pLysE or pLysH reduce the fully induced activity of T7 RNA polymerase such that induced cells can continue to grow and produce innocuous target proteins indefinitely. Different configurations of the expression system can maintain several different steady-state levels of target gene expression. The presence of T7 lysozyme has the further advantage of facilitating the lysis of cells in preparing extracts for purification of target gene products.
噬菌体T7溶菌酶是T7 RNA聚合酶的天然抑制剂，它可以降低T7 RNA聚合酶诱导型基因的基础活性，并使相对毒性较强的基因在T7启动子的控制下在同一细胞中得以稳定表达。与用于从T7启动子表达基因的pET载体兼容的质粒pLysS或pLysL所提供的低水平T7溶菌酶，足以稳定许多目标质粒，并且在诱导T7 RNA聚合酶后仍能产生高水平的目标蛋白。质粒pLysE或pLysH所提供的较高水平的溶菌酶会降低T7 RNA聚合酶的完全诱导活性，从而使诱导的细胞能够继续生长并无限期地产生无害的目标蛋白。表达系统的不同配置可以维持几种不同的目标基因表达稳态水平。T7溶菌酶的存在还有一个额外的优点，即便于在制备用于纯化目标基因产物的提取物时使细胞裂解。
