BL21Cells

The following cells are for expression of toxic proteins.

BL21 Star (DE3)pLysS

F- ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) pLysS (CamR), from Invitrogen, Cat #: C6565-03

The pLysS plasmid carried by the BL21 StarTM(DE3)pLysS strain produces T7 lysozyme 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 pUC- or pBR322-derived plasmids. It requires IPTG to induce expression of the T7 RNA polymerase from the lacUV5 promoter.

RNaseE (rne131), which is one of the major sources of mRNA degradation. BL21 Star cells significantly improve the stability of mRNA transcripts and increase protein expression yield from T7 promoter-based vectors due to rne131 mutation.

Rosetta(DE3)pLysS

Novagen, EMD Biosciences

F- ompT hsdSB(rB- mB-) gal dcm (DE3) pLysSpRARE2 (Cam-R)

Rosettacells have tRNAs for the codons AUA, AGG, AGA, CUA, CCC, and GGA on a compatible chloramphenicol-resistant plasmid, pRARE. pLysS is a chloramphenicol-resistant plasmid with a P15A replicon that encodes T7 lysozyme, which is for inhibiting T7 RNA polymerase. pLysSRARE and pLysSRARE2 contain a CamR plasmid (pACYC184) that carries the gene for T7 lysozyme plus tRNA genes for several codons rarely used in E. coli.

Lemo21(DE3)

NEB. Cat # C2528H.

fhuA2 [lon] ompT gal (λ DE3) [dcm] ∆hsdS/ pLemo(CamR)

λ DE3 = λ sBamHIo ∆EcoRI-B int::(lacI::PlacUV5::T7 gene1) i21 ∆nin5

pLemo = pACYC184-PrhaBAD-lysY

Lemo21(DE3) offers the host features of BL21(DE3) while also allowing for tunable expression of difficult clones. Tunable expression is achieved by varying the level of lysozyme (lysY), the natural inhibitor of T7 RNA polymerase. The level of lysozyme is modulated by adding L-rhamnose to the expression culture at levels from zero to 2000 µM. When Lemo21(DE3) is grown without rhamnose, the strain performs the same as a pLysS containing strain. However, optional addition of rhamnose tunes the expression of the protein of interest. For difficult soluble proteins, tuning the expression level may also result in more soluble, properly folded protein.

OverExpress C41(DE3) and C43(DE3)

Lucigen, 60448-1, 60446-1

C41(DE3) was derived from BL21(DE3). This strain has at least one 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).