Shop All Expression Competent Cells

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

BL21(DE3)pLysE E. coli are ideal for use with T7 promoter-based expression vectors. Like BL21(DE3)pLysS E. coli, BL21(DE3)pLysE carry the lambda DE3 lysogen. In addition, BL21(DE3)pLysE cells contain the pLysE plasmid, which constitutively expresses T7 lysozyme. T7 lysozyme reduces the basal expression of target genes by inhibiting T7 RNA polymerase. The pLysE plasmid in BL21(DE3)pLysE expresses higher levels of T7 lysozyme than the pLysS plasmid in BL21(DE3)pLysS.
The BL21(DE3)pLysE strain provides tighter control of T7 RNA polymerase, which is necessary when the recombinant protein to be expressed is toxic.

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

BL21(DE3)pLysS cells are ideal for use with T7 promoter-based expression systems (e.g., pRSET, pCR™T7, and pET). BL21(DE3)pLysS E. coli carry both the DE3 lysogen and the plasmid pLysS. pLysS constitutively expresses low levels of T7 lysozyme, which reduces basal expression of recombinant genes by inhibiting basal levels of T7 RNA polymerase.

PichiaPink™ Expression Strain Set (Invitrogen™)

The PichiaPink™ Expression Strain Set contains the 4 Pichia pastoris strains for use with the PichiaPink™ Expression System Kits. Each strain comes as a frozen stock in YPD media with 15% glycerol. All PichiaPink™ strains have the ade2 deletion. 3 strains have deletions of two protease genes, PEP4 and PRB1. You can use the PichiaPink™ Expression Strain Set to refill your PichiaPink™ Yeast Expression System Kits.

The PichiaPink™ Expression Strain Set includes the following Pichia strains:
•     PichiaPink™ Strain 1: ade2
•     PichiaPink™ Strain 2: ade2, pep4
•     PichiaPink™ Strain 3: ade2, prb1
•     PichiaPink™ Strain 4: ade2, prb1, pep4

Select Transformants by Color
The PichiaPink™ Yeast Expression System makes it easy to select for transformed colonies by color. Untransformed PichiaPink™ strains form pink colonies. When grown on plates without adenine, transformed PichiaPink™ strains form white colonies (Fig 1).

Get Reduced Protein Degradation
The PichiaPink™ Expression Strain Set comes with 3 strains that include knockouts in two protease genes. Protease-deficient strains reduce the need for protease inhibitors when growing your cells and improve the yield of your protein. Test a single protease knockout or the double protease knockout to find the one that works best for you.

Why Choose the PichiaPink™ Yeast Expression System?
The PichiaPink™ Yeast Expression System is based on the yeast Pichia pastoris. Advantages of Pichia pastoris include rapid growth, well-defined genetic background, simple media formulation, and easy handling. For over 30 years, Pichia pastoris has been used by labs around the world for producing hundreds of different proteins from many species including human (Ref 1, 2). The PichiaPink™ Yeast Expression System allows convenient and cost-effective protein production from small to large scales.

For information on obtaining a commercial-use license for the PichiaPink™Yeast Expression System, please inquire at outlicensing@lifetech.com.

For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.

Related Links
Learn more about the PichiaPink™ Yeast Expression System.
Learn more about our other protein expression systems.

References

1. Cereghino JL, Cregg JM. Heterologous protein expression in the methylotrophic yeast Pichia pastoris. FEMS Microbiol Rev. 2000 Jan;24(1):45-66. [PubMed]
2. Cereghino GP, Cereghino JL, Ilgen C, Cregg JM. Production of recombinant proteins in fermenter cultures of the yeast Pichia pastoris. Curr Opin Biotechnol. 2002 Aug;13(4):329-32. [PubMed]

BL21-AI™ One Shot™ Chemically Competent E. coli (Invitrogen™)

One Shot® BL21-AI™ E. coli are chemically competent cells designed for applications that require tight regulation and strong expression of toxic proteins from any T7 promoter-based expression systems. One Shot® BL21-AI™ Chemically Competent cells have a transformation efficiency of >1×108 cfu/ µg plasmid DNA.
• Ideal for inducing expression of toxic protein
• Gene expression is regulated by the addition of L-arabinose to culture
• Suitable for use with any T7 promoter-based plasmids
• Supplied in a convenient One Shot® format

Excellent Expression of Toxic Recombinant Proteins
One Shot® BL21-AI™ E. coli contains a chromosomal insertion of the gene encoding T7 RNA polymerase (T7RNAP) into the araB locus of the araBAD operon, placing regulation of T7 RNAP under the control of the arabinose-inducible araBAD promoter (1). Therefore, this strain is especially useful for the expression of genes that may be toxic to other BL21 strains where basal expression of T7 RNAP is leaky. The BL21-AI™ strain does not contain the Ion protease and is deficient in the outer membrane protease, OmpT. This genotype reduces degradation of heterologous proteins expressed in this strain. Finally, the yield of recombinant protein obtained from BL21-AI™ is generally similar to that obtained from other BL21 strains.

Genotype:
F-ompT hsdSB (rB- mB-) gal dcm araB::T7RNAP-tetA

Easy-to-use, Single Tube Format
The single tube, single use, format allows for all transformation steps to take place in the same tube, thereby helping to save time and prevent contamination.

Find the Strain and Format That You Need
We also offer many other different strains and formats of chemically competent cells and electrocompetent cells to help meet your specific transformation needs. For expression of non-toxic recombinant proteins, choose our One Shot® BL21 Star™ (DE3) chemically competent cells or One Shot® BL21 Star™ (DE3) pLysS chemically competent cells.

For Research Use Only. Not intended for animal or human diagnostic or therapeutic use.

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 (e.g., Champion™ pET vectors). One Shot® BL21 Star™ (DE3) Chemically Competent cells are provided at a transformation efficiency of 1 x 108 cfu/µg plasmid DNA. Features of One Shot® BL21 Star™ cells:

• Contain a genotype that promotes high mRNA stability and protein yield
• Optimized for use with low copy number, T7 promoter-based plasmids
• Provided in a single-tube, single-use format—allows all transformation steps to take place in the same tube, thereby helping to save time and prevent contamination

Enhanced expression of nontoxic recombinant proteins
One Shot® BL21 Star™ (DE3) cells contain the DE3 lysogen that carries the gene for T7 RNA polymerase under control of the lacUV5 promoter. IPTG is required to induce expression. This strain also 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. Protein expression is further enhanced by the absence of the lon and outer membrane (OmpT) proteases, which reduces degradation of heterologous proteins.

Note: The BL21 Star™ strains have higher basal expression of heterologous genes than BL21 strains, due to the increased stability of mRNA. Therefore, these strains may not be useful for expression of toxic genes.

Genotype:F-ompT hsdSB (rB-, mB-) galdcmrne131 (DE3)

Find the strain and format that you need
We also offer many other different strains and formats of chemically competent cells and electrocompetent cells to help meet your specific transformation needs. For expression of toxic proteins, consider BL21-AI™ One Shot® Chemically Competent E. coli.

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

One Shot® BL21 Star™ (DE3) pLysS E. coli are chemically competent cells designed for applications that require high-level expression of non-toxic recombinant proteins from high copy number, T7 promoter-based expression systems (e.g., pRSET T7 vectors). One Shot® BL21 Star™ (DE3) pLysS Chemically Competent cells have a transformation efficiency of >1 x 108 cfu/ µg plasmid DNA.
• High mRNA stability results in increased protein yield
• Ideal for use with high copy number, T7 promoter-based plasmids
• Low background expression in uninduced cells

Increased mRNA Stability Improves Protein Yield
One Shot® BL21 Star™ (DE3) pLysS E. coli offers enhanced mRNA stability so that abundant mRNA is available for protein expression. This enhanced stability is due to a mutation in the RNaseE gene (rne131), which is involved in mRNA degradation.

High Expression of Non-Toxic Recombinant Proteins
One Shot® BL21 Star™ (DE3) pLysS cells are ideal for high-level expression of non-toxic but potentially growth-inhibiting recombinant proteins from high copy number, T7 promoter-based expression systems. 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 also contains the DE3 lysogen that carries the T7 RNA polymerase gene under control of the lacUV5 promoter, and IPTG is required to induce expression of the T7 RNA polymerase. One Shot® BL21 Star™ (DE3) pLysS cells do not contain the lon protease and are also deficient in the outer membrane protease, OmpT. The absence of these proteases reduces degradation of heterologous proteins.

Note: The BL21 Star™ strains have higher basal expression of heterologous genes than BL21 strains, due to the increased stability of mRNA. Therefore, these strains may not be useful for expression of toxic genes. However, the BL21 Star™ (DE3) pLysS strains offer lower expression levels than the BL21 Star™ strains.

Genotype:
F-ompT hsdSB (rB-, mB-) galdcmrne131 (DE3) pLysS (CamR)

Easy-to-use, Single Tube Format
The single tube, single use, format allows for all steps of transformation up to plating to take place in the same tube, thereby helping to save time and prevent contamination.

Find the Strain and Format That You Need
We also offer many other different strains and formats of chemically competent cells and electrocompetent cells to help meet your specific transformation needs. For expression of toxic proteins, choose BL21-AI™ One Shot® Chemically Competent E. coli. For expression of non-toxic recombinant proteins from low copy number (e.g. Champion™ pET vectors), T7 promoter-based expression system, choose our One Shot® BL21 Star™ (DE3) chemically competent cells.

For Research Use Only. Not intended for animal or human diagnostic or therapeutic use.

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

One Shot® BL21(DE3) Chemically Competent E. coli are ideal for use with bacteriophage T7 promoter-based expression systems (e.g., pRSET, pCR™T7, and pET). BL21(DE3) cells carry the lambda DE3 lysogen. Recombinant proteins that are nontoxic to E. coli are generally expressed at higher levels in BL21(DE3) cells than in BL21(DE3)pLysS or BL21(DE3)pLysE. However, the basal expression levels of heterologous genes are significantly higher in BL21(DE3) than in BL21(DE3)pLysS or BL21(DE3)pLysE.

About BL21 strains
BL21 strains are descended from the E. coli B strain and have been specifically constructed for high-level expression of recombinant proteins. These strains have two important attributes that make them ideal for protein expression: key genetic markers and inducibility of protein expression. The most important genetic markers help recombinant RNA and/or protein accumulate to high levels without degradation. Inducibility helps to minimize the toxic effects of some recombinant proteins.