71060  RosettaBlue™(DE3)pLacI Competent Cells

Expression host strains for pETBlue™ and pTriEx™ vectors are lDE3 lysogens that also carry the compatible pLacI plasmid, encoding the lac repressor. The pLacI plasmid confers chloramphenicol resistance and provides enough lac repressor to inhibit transcription from the T7lac promoter in the absence of inducer. The NovaBlue host strain is recommended for initial cloning with pETBlue and pTriEx vectors due to its superior transformation efficiency and high yields of high-quality plasmid DNA.

Note that these strains are not recommended for use with pET, pACYCDuet™, pCDF, pRSF, pCOLADuet™ or pETcoco™ vectors.

.RosettaBlue™ host strains are NovaBlue derivatives that combine high transformation efficiency and recA endA lacI^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. 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. In RosettaBlue(DE3)pLacI, the rare tRNA genes are present on the same plasmid that carries the lac repressor gene.

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. Genotype: endA1 hsdR17 (r_K12^– m_K12⁺) supE44 thi-1 recA1 gyrA96 relA1 lac (DE3) F′[proA⁺B⁺ lacI^qZΔM15::Tn10] pLacIRARE (Cam^R, Tet^R)