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

One Shot BL21 Star (DE3) Chemically Competent E. coli are designed for applications that require high-level expression of non-toxic recombinant proteins from low copy number, T7-promoter-based expression systems such as Champion pET vectors. 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 strain has higher basal expression of heterologous genes than BL21 (DE3) strains, due to the increased stability of mRNA. Thus, strains such as BL21-AI are recommended for toxic protein expression. One Shot BL21 Star (DE3) Chemically Competent cells are provided at a transformation efficiency of >1 x 10⁸ cfu/μg plasmid DNA.

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 strain. Additionally, several other strain features make it 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.

The BL21 (DE3) E. coli strain is one of the most popular host strains used to produce recombinant proteins and adapted in research or industrial applications. This strain has been engineered to carry the λDE3 lysogen that contains the T7 RNA polymerase gene under the control of the lacUV5 promoter. IPTG is required to induce expression of the T7 RNA polymerase cascade system that in turn transcribes the T7-promoter-regulated target gene.

One Shot BL21 Star (DE3) 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
• Optimized for use with low copy number, T7-promoter-based plasmids
• rne131 mutation that reduces levels of endogenous RNases and mRNA degradation
• 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 Star (DE3) 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)

Find the strain and format that fits your needs
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.