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Name BL21(DE3)
Genotype E. coli B dcm ompT hsdS(rB-mB-) gal
Phage λDE3
Sources LMBP 1455
References PMID: 3537305


The strain contains DE3, a λ prophage carrying the T7 RNA polymerase gene under control of the lac UV5 promoter and lacIq. IPTG is required to induce expression of the T7 RNA polymerase. Protein expression from transforming plasmids containing a T7 promoter-driven expression system is repressed until IPTG induction of T7 RNA polymerase expression occurs. The strain does not contain the lon protease and is also deficient in the outer membrane protease, OmpT. The lack of two key proteases reduces the degradation of heterologous proteinsexpressed in the strain.