Tuner strains are lacZY deletion mutants of BL21 and enable adjustable levels of protein expression throughout all cells in a culture. The lac permease (lacY) mutation allows uniform entry of IPTG into all cells in the population, which produces a concentration-dependent, homogeneous level of induction. By adjusting the concentration of IPTG, expression can be regulated from very low levels up to the robust, fully induced levels commonly associated with pET vectors. Lower-level expression may enhance the solubility and activity of difficult target proteins. DE3 indicates that the host is a lysogen of λDE3, and therefore carries a chromosomal copy of the T7 RNA polymerase gene under control of the lacUV5 promoter. Such strains are suitable for production of protein from target genes cloned in pET vectors by induction with IPTG. pLysS strains express T7 lysozyme, which further suppresses basal expression of T7 RNA polymerase prior to induction, thus stabilizing pET recombinants encoding target proteins that affect cell growth and viability. Genotypes: Tuner F– ompT hsdSB (rB– mB–) gal dcm lacY1 Tuner(DE3) F– ompT hsdSB (rB– mB–) gal dcm lacY1(DE3) Tuner(DE3)pLysS F– ompT hsdSB (rB– mB–) gal dcm lacY1(DE3) pLysS (CamR)，官网链接：https://www.sigmaaldrich.cn/product/mm/70726m 默克 科研、开发、生产。 作为生命科学行业的全球领先供应商，我们致力于为科研、生物技术开发和生产，以及制药药物疗法开发和生产提供各类解决方案和服务。

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