Transform the way you think about protein expression...in E. coli
Capabilities beyond BL21, simplicity beyond baculovirus and mammalian cell expression
BL21 and beyond
Novagen first commercialized BL21 in 1990 and it has remained the gold standard among expression hosts ever since. Being deficient in both lon and ompT proteases, BL21 and its derivatives are the most popular hosts today. Yet, a number of other Novagen host strains are available, as lDE3 lysogens for T7 promoter-driven expression, and as non-lDE3 lysogens for expression from E. coli promoters. These state-of-the-art strains are powerful tools for situations more challenging than BL21 can support, particularly the expression of mammalian proteins in E. coli. This online spotlight guide can help you select the best host strain for your protein and your application.
Factors influencing protein expression
Three factors influence protein expression:
the expression vector, the host cell, and the growth and induction conditions.
Changing one or more of these factors can dramatically affect expression levels and target protein solubility.
Vector-host relationship
Any number of systems may be suitable for expression of analytical amounts of some proteins for screening, yet only one combination of vector, host strain, and culture conditions may work best for other proteins, for activity assays, and for larger-scale production. To produce a high yield of active protein, set up a test matrix of vector, host, and culture conditions to empirically determine the optimal result. Optimize conditions using competent cell sets, Quarters™ Competent Cells, and QuarterPack™ Competent Cell Arrays.
Compatibility matrix
Novagen host strains are compatible with a variety of expression vectors, as long as the plasmid replicon and antibiotic resistance markers are distinct from corresponding elements carried by the host.
Antibiotic Resistance(s)
Host strain
Replicon
Cam
Kan
Rif
Tet
contains pLysS
P15A
Yes
contains pLacI
P15A
Yes
Rosetta 2
P15A
Yes
Origami 2
F
Yes
Rosetta-gami 2
P15A + F
Yes
Yes
BL21
none
none
NovaBlue
F
Yes
Origami B
none
Yes
Yes
RosettaBlue
P15A + F
Yes
Yes
Rosetta-gami B
P15A
Yes
Yes
Yes
Tuner
none
none
BLR
none
Yes
HMS174
none
Yes
Effect of vector/host combination on expression levels of two proteins
The indicated cell cultures were grown at 37°C to OD600 of approximately 0.8 and expression induced with 1 mM IPTG for 2.5 h. Total cell protein samples were run with the Novagen Perfect Protein™ Markers on a 4–20% gradient SDS-PAGE followed by staining with Coomassie blue. Vectors used were pET-20b(+) and pET-22b(+) for the recombinant antibody and pET-23b(+) and pET-21b(+) for p53.
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Solve complex problems using E. coli
Novagen host strains provide you with a range of technical solutions to help you avoid eukaryotic expression as well as the frustrations of obtaining aggregated protein, inactive protein or even no protein at all.
Protein expression troubleshooting guide
Symptom
Possible issue
Solution
Suggested host
No protein
E. coli codon usage (codon bias)
Supply rare tRNAs
Rosetta 2 Rosetta-gami 2 Rosetta-gami B RosettaBlue
