One Shot™ BL21(DE3)pLysS Chemically Competent E. coli (Invitrogen™)

One Shot BL21(DE3)pLysS Chemically Competent E. coli cells are ideal for use with bacteriophage T7 promoter-based expression systems such as pRSET and pET. The pLysS plasmid carried by the BL21(DE3) pLysS strain produces T7 lysozyme, an inhibitor of T7 RNA polymerase, to reduce basal level expression of the gene of interest. pLysS confers resistance to chloramphenicol (CamR) and contains the p15A origin. This origin allows pLysS to be compatible with plasmids containing the ColE1 or pMB1 origin (i.e. pUC- or pBR322- derived plasmids). Recombinant proteins that are nontoxic to E. coli are generally expressed at higher levels in BL21(DE3) cells compared to the BL21(DE3) pLysS strain with tighter expression control. BL21(DE3)pLysS is recommended for use when expressing toxic genes.

The BL21 (DE3) E. coli strain is one of the most popular host strains to produce recombinant proteins. This strain had been engineered to carry the λDE3 lysogen that contains T7 RNA polymerase gene under control of the lacUV5 promoter. IPTG is required to induce expression of the T7 RNA polymerase cascade system that in turn transcribe T7 promoter regulated target gene.

BL21(DE3) is a derivative from the E. coli B strain that does not contain the ion protease and is also deficient in the outer membrane protease OmpT. The lack of two key proteases reduces degradation of heterologous proteins expressed in the strains. Additionally, several other strain features make them especially suited for protein production, namely fast growth in minimal medium, a lower acetate production when grown in high glucose media, and an ability to reach high cell density. One Shot BL21(DE3)pLysS Chemically Competent E. coli cells can achieve transformation efficiency of >1 x 10⁸ cfu/μg of control DNA.

One Shot BL21(DE3)pLysS Chemically Competent E. coli cells offer:
• Transformation efficiency of >1 x 10⁸ cfu/μg control plasmid DNA
• Ion and OmpT protease deficiency that reduces degradation of recombinant protein
• IPTG-inducible lacUV5 promoter that controls expression of the T7 RNA polymerase
• pLysS (CamR) plasmid for reduced basal expression in uninduced cells
• hsdS mutation that allows efficient transformation of unmethylated DNA
• Fast growth in minimal medium and ability to reach high cell density

Easy-to-use One Shot format
BL21(DE3)pLysS Chemically Competent E. coli cells are supplied in the convenient, single-reaction One Shot format. The single-tube, single-use format allows all steps of the transformation protocol, up to plating, to take place in the same tube, thereby helping save time and to prevent contamination.

Genotype
F^–ompT hsdSB (r_B–, m_B–) gal dcm (DE3) pLysS(CamR) 

Find the strain and format that you need
We offer other E. coli strains for protein expression.
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BL21 Star (DE3) and other strains are available in MultiShot formats for high throughput applications.
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We offer a variety of systems for the expression of recombinant proteins in E. coli. The Champion pET expression system provides the highest level of protein production available in any expression system.