One Shot BL21 Star (DE3)pLysS Chemically Competent E. coli are cells designed for applications that require high-level expression of non-toxic recombinant proteins from low or high copy number vectors, such as pRSET and pET. The BL21 (DE3) E. coli strain is one of the most popular host strains to produce recombinant proteins and is adapted for research and industrial applications (e.g., first biopharmaceutical recombinant human insulin).

BL21(DE3) is a derivative of the E. coli B strain that does not contain the lon 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 made them especially suited for protein production, namely fast growth in minimal medium, a lower acetate production when grown in high glucose media, and the ability to reach high cell density.

This strain was 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. The pLysS CamR plasmid carried by the BL21 Star (DE3) pLysS strain expresses T7 lysozyme, a T7 RNA polymerase inhibitor that prevents leaky expression in uninduced cells. The p15a origin of pLysS makes this plasmid compatible with pUC or pBR322-derived plasmids.This strain offers enhanced mRNA stability due to a mutation in the RNaseE gene (rne131) that reduces levels of endogenous RNases and mRNA degradation, thereby increasing the stability of mRNA transcripts and increasing protein yield. The BL21 Star (DE3) pLys strain has lower basal expression of heterologous genes than BL21 Star (DE3) strain. Other trains such as BL21-AI are recommended for toxic protein expression. One Shot BL21 Star (DE3) pLysS Chemically Competent cells have a transformation efficiency of >1 x 10⁸ cfu/μg plasmid DNA.

One Shot BL21 Star (DE3)pLysS Chemically Competent E. coli offer:
• Transformation efficiency of >1 x 10⁸ cfu/μg plasmid DNA
• Ion and OmpT protease deficiency reduces degradation of recombinant protein
• IPTG-inducible lacUV5 promoter controls expression of the T7 RNA polymerase
• rne131 mutation reduces levels of endogenous RNases and mRNA degradation
• pLysS (CamR)plasmid for reduced basal expression in uninduced cells
• hsdS mutation 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 Star (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 prevent contamination.

Genotype
F^-ompT hsdSB (r_B^-, m_B^-) gal dcm rne131 (DE3) pLysS (CamR)

Find the strain and format that you need
We offer other E. coli strains for protein expression.
For expression of toxic proteins, consider BL21-AI One Shot Chemically Competent E. coli.
BL21 Star (DE3) and other strains are available in MultiShot formats for high throughput applications.
Explore bacterial growth media formats.
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.