KMD Bioscience Co., Ltd.
400-621-6806
2023-01-30 Hits(839)
Host, vector, and culture conditions (including cultivation media) are considered among the three main elements contributing to a successful production of recombinant proteins. Accordingly, one of the most common hosts to produce recombinant proteins is Escherichia coli. Numerous modifications have been carried out on Escherichia coli to optimize it as a good candidate for protein expression and as a result, several engineered strains of Escherichia coli have been designed.
BL21 and BL21(DE3)
Both BL21 and BL21 (DE3) are from E.coli B strains and have defects in the genes of Lon protease (cytoplasm) and OmpT protease (outer membrane). BL21 includes only E.coli RNA polymerase, while BL21 (DE3) has λDE3 lysogen which contains T7 RNA polymerase under the control of LacUV5 promoter. Therefore, BL21 can be only recruited for expressing proteins with E.coli RNA polymerase promoter (lac, tac, trc, ParaBAD, PrhaBAD, and T5) in the up-stream of their genes; while BL21 (DE3) can be similarly used for expressing proteins with T7 promoter within the upstream of their genes.
Rosetta (BL21 CodonPlus)
The scarcity of special tRNAs in E.coli can largely restrict efficient production of heterologous proteins. When expressing eukaryotic genes in the prokaryotic system, some codons in eukaryotic genes may be rare for prokaryotic cells, resulting in low expression efficiency and expression levels. Rosetta host strains are BL21 lacZY (Tuner (DE3)) derivatives designed to enhance the expression of eukaryotic proteins that contain codons rarely used in E. coli. These strains can supply tRNAs for AGG, AGA, AUA, CUA, CCC, GGA, CGG codons on a compatible chloramphenicol-resistant plasmid (pRARE/pRARE2).
Figure 1 Schematic view of three types of E.coli strains (BL21, BL21(DE3) and Rosetta(DE3)) used in recombinant protein production.
|
Bacterial Strain |
Features |
Promoter (Vector) |
Benefit |
|
BL21 |
*Deficient in lon and ompT proteases
*Induced by IPTG |
tac (pGEX/pMAL) |
Suitable for the expression of toxic genes |
|
BL21(DE3) |
*Has DE3 lysogen that expresses T7 RNA polymerase
*Deficient in lon and ompT proteases
*Induced by IPTG |
T7 (pET/pGEX/pMAL) |
Suitable for the expression of nontoxic genes |
|
Rosseta |
*BL21 lacZY (Tuner(DE)) derivatives which has DE3 lysogen that expresses T7 RNA and has lac permease (lacY) mutation
*Has additional copies of genes encoding the tRNAs for rare codons
*Induced by IPTG |
T7 (pET) |
Suitable for the expression heterogeneous proteins |
Table 1 E.coli strains (BL21, BL21(DE3) and Rosetta(DE3)) used as expression host.
References:
Hayat, S. M., Farahani, N., Golichenari, B., & Sahebkar, A. (2018). Recombinant protein expression in Escherichia coli (E. coli): what we need to know. Current pharmaceutical design, 24(6), 718-725.
FL-4, Building A5, International Enterprise Community, Tianjin, China
Email：[email protected]
Hot Line： +86-022-82164980
Technical Support：[email protected]
