Description
EXPRESS BL21(DE3) strains contain the phage T7 RNA polymerase gene linked to the IPTG-inducible promoter, for use with any expression plasmid containing the T7 promoter (e.g., pET or pSMART®-cDNA vectors). EXPRESS pLysS Cells also produce T7 lysozyme to repress low-level transcription from the T7 promoter prior to IPTG induction, helping to stabilize inserts. EXPRESS pLysE Cells have a higher level of repression by T7 lysozyme, offering the greatest control over expression of inserts. EXPRESS BL21(DE3) Chemically Competent Cells are optimal for routine protein expression.