OverExpress C43 (DE3) Chemically Competent Cells (SOLOS) > 1 x 10e6 cfu/ug

Product Description

• Effective in expressing toxic membrane proteins
• Recommended for membrane proteins with T7 vector
• Available from OverExpress product line:
  - 4 Chemical Competent strains: C41(DE3), C41(DE3)pLysS, C43(DE3) & C43(DE3)pLysS
  - ChemComboPack
  -2 Electrocompetent strains: C41(DE3), & C43(DE3)

OverExpress Chemically Competent Cells are E. coli strains that are effective in expressing toxic proteins from all classes of organisms, including eubacteria, yeasts, plants, viruses, and mammals. The effectiveness of these strains in expressing toxic proteins has been validated in more than 350 publications.

As in standard BL21(DE3) strains, OverExpress C43(DE3) is a lysogen of λDE3. It carries a chromosomal copy of the T7 RNA Polymerase gene under the control of the lacUV5 promoter. The strain is suitable for production of protein from target genes cloned into T7-driven expression vectors. Strain C43(DE3) was derived from C41(DE3) by selecting for resistance to a different toxic protein. It carries at least one additional mutation that provides a greater level of tolerance to toxic proteins. As C41(DE3 it is also deficient in the lon and ompT proteases.

Features

Transformation Efficiency ≥ 1 x 10⁶ cfu/µg pUC19

Genotype

F^- ompT hsd S_B (r^- m_B^-) gal dcm (DE3)

Supporting Data

The OverExpress strains contain genetic mutations phenotypically selected for conferring tolerance to toxic proteins. The strain C41(DE3) was derived from BL21(DE3). This strain has at least one uncharacterized mutation, which prevents cell death associated with expression of many recombinant toxic proteins. The strain C43(DE3) was derived from C41(DE3) by selecting for resistance to a different toxic protein and can express a different set of toxic proteins to C41(DE3). Figure 1 graphically illustrates the advantages of the OverExpress Competent Cells, compared to standard BL21(DE3) cells, in expressing toxic proteins.

Figure 1. Green Fluorescent Protein (top) or Red Fluorescent Protein (bottom) expressed from a T7 promoter construct that was transformed into C41, BL21, or C43 competent cells spread on IPTG plates to induce protein expression.

Table. 1 and Figure. 2 summarise transformation effectiveness, tolerance of expression-induced toxicity, and protein expression for T7 expression plasmids coding for a variety of recombinant proteins. These results demonstrate that the OverExpress C41(DE3) and C43(DE3) strains are clearly superior to the parental BL21(DE3) in transformation and expression of toxic proteins.

Table 1. Comparison of OverExpress C41(DE3) and C43(DE3) cells with the parental strain BL21(DE3) in transformation and expression of heterologous proteins.**

Figure 2. Comparison of OverExpress C41(DE3) and C43(DE3) cells with the parental strain BL21(DE3) in transformation and expression of heterologous proteins.**

^a Transformation success corresponds to the presence of colonies on LB+ampicillin agar following transformation with a plasmid.
^b Expression toxicity corresponds to the absence of colonies on LB+ampicillin+IPTG agar following transformation with a plasmid.
^c Expressing plasmids corresponds to observation of a heterologous protein in the total cell pellet on Coomassie-stained SDS-PAGE following growth of a colony in LB+ampicillin medium and induction with IPTG.
**L. Dumon-Seignovert, G. Cariot, and L. Vuillard (2004). Protein Expression and Purification 37, 203-206. Data used with permission.

Which OverExpress cell strain should I use?

It is difficult to predict which of the four OverExpress strains – C41(DE3), C43(DE3), C41(DE3)pLysS, or C43(DE3)pLysS – will work best in expressing a given protein. We recommend initially using the OverExpress ComboPack™, which contains 3 reactions each of the four OverExpress competent cell strains, to determine which one is best for your application.

OverExpress Genotypes

OverExpress C41(DE3): F^– ompT hsdSB (rB- mB-) gal dcm (DE3)

OverExpress C41(DE3)pLysS: F^– ompT hsdSB (rB- mB-) gal dcm (DE3) pLysS (CmR)

OverExpress C43(DE3): F^– ompT hsdSB (rB- mB-) gal dcm (DE3)

OverExpress C43(DE3)pLysS: F^– ompT hsdSB (rB- mB-) gal dcm (DE3) pLysS (CmR)