FAQ: What E. coli expression strains are available?

NEB offers several E. coli strains for protein expression. BL21(DE3) (NEB #C2527) is offered for routine T7 expression and BL21 (NEB #C2530) for non-T7 expression. NiCo21(DE3) (NEB #C2529) is recommended for the expression of His-tagged proteins to improve target protein purity. NEB Express (NEB #C2523) is an enhanced BL21 derivative and NEB Express Iq (NEB #C3037) offers controlled expression from vectors with lac, tac, trc or T5-lacO promoters. T7 Express Competent E. coli (NEB #C2566), T7 Express lysY (NEB #C3010) and T7 Express lysY/Iq (NEB #C3013) offer enhanced performance and higher transformation efficiency relative to BL21(DE3). The lysY feature is a unique offering which provides exceptional control of T7 expression. NEB also offers 4 Shuffle Competent E. coli strains which are capable of correctly folding proteins with multiple disulfide bonds. This capability is enabled by cytoplasmic expression of DsbC disulfide bond isomerase. Finally, Lemo21(DE3) (NEB #C2528)  is available for tunable T7 expression of difficult targets such as membrane proteins, toxic proteins and proteins prone to insoluble expression.