C2528J, Lemo21(DE3) Competent E.coli - 12 transformation reactions (12 tubes)

Chemically competent E. coli cells suitable for transformation and protein expression. Fine tuning of T7 expression can alleviate inclusion body formation or growth inhibitory effects from toxic proteins. In many cases, less expression equals more protein of interest produced in the desired form. This is particularly true for membrane protein expression. Membrane protein expression and protein export in E. coli are both limited by the throughput capacity of the Sec translocase and in some cases the Tat translocase. T7 expression of proteins targeted to the Sec translocase often leads to accumulation of inclusion bodies or inhibition of cell division if expression is not regulated. 

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.

Highlights

• BL21(DE3) containing the Lemo System™
• Tunable T7 Expression Strain for difficult targets: membrane proteins, toxic proteins and proteins prone to insoluble expression
• Deficient in proteases Lon and OmpT
• Resistant to phage T1 (fhuA2)
• Lemo System™ maintained by chloramphenicol

Transformation Efficiency

1–3 x 10⁷ cfu/µg pUC19 DNA

Genotype

fhuA2 [lon] ompT gal (λ DE3) [dcm] ∆hsdS/ pLemo(Cam^R)  λ DE3 = λ sBamHIo ∆EcoRI-B int::(lacI::PlacUV5::T7 gene1) i21 ∆nin5 pLemo = pACYC184-PrhaBAD-lysY