BL21 (DE3) pLysE - Discontinued

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Chemically competent E. coli cells suitable for transformation and protein expression. This strain contains the T7 RNA polymerase gene to provide the highest level of repression of potentially toxic gene products.

Features & Benefits

  • High efficiency - available in ≥107 cfu/μg, perfect for routine subcloning
  • Protease deficient - facilitates the isolation of intact recombinant proteins
  • T7 Promoter - lowest background expression of target genes
  • Convenient size - small aliquots reduce waste


Highest repression of basal T7 promotor expression.


BL21(DE3)pLysE competent cells are chemically competent cells used for high-level protein expression under the control of a T7 promoter. Like BL21(DE3)pLysS E. coli, BL21(DE3)pLysE is lysogenic for λ-DE3 but, 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.


Genotype: F- ompT hsdSB(rB-mB-) gal dcm (DE3)pLysE (CamR)




Chemically Competent Cells

10 x 100µl

pUC19 control vector (100pg/µl)


Storage & Stability

All kit components should be stored at -80°C upon receipt. When stored under the recommended conditions and handled correctly, full activity of the kit is retained until the expiry date on the outer box label.

Shipping conditions

Shipped on Dry Ice or Blue Ice.

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