MilliporeSigma™ Novagen™ RosettaBlue™ (DE3)pLysS Competent Cells

RosettaBlue™ host strains are NovaBlue derivatives that combine high transformation efficiency and recA endA lacI&superscript_q; mutations with enhanced expression of eukaryotic proteins that contain codons rarely used in E. coli. These strains supply tRNAs for AGG, AGA, AUA, CUA, CCC, and GGA on a chloramphenicol-resistant plasmid. The tRNA genes are driven by their native promoters. In RosettaBlue(DE3)pLysS, the rare tRNA genes are present on the same plasmid that carries the T7 lysozyme gene. Blue/white screening is not possible with RosettaBlue(DE3) strains due to the presence of the lacZ α-peptide coding sequence in the λDE3 prophage. DE3 indicates that the host is a lysogen of λDE3, and therefore carries a chromosomal copy of the T7 RNA polymerase gene under control of the lacUV5 promoter. Such strains are suitable for production of protein from target genes cloned in pET vectors by induction with IPTG. pLysS strains express T7 lysozyme, which further suppresses basal expression of T7 RNA polymerase prior to induction, thus stabilizing pET recombinants encoding target proteins that affect cell growth and viability.