A protocol for protein expression mention they used BL21 gold cells, but I'm a bit confused after looking for them in suppliers - sometimes they are mentioned as if they were a specific type of cell, sometimes it seems it is a collective term for modified BL21 strains which would include, for example, the pLyss cells. Could someone clarify this?
Dear Luckas
BL21 is a E.coli strain derived from E.coli type B strains (and not K-12 as happen for the most other strains suitable for cloning e.g DH5aplha). Characteristics such as protease deficiency (lon and ompT proteases), often regarded as common characteristics among B lineage, has driven the development of those strains for protein expression host.
Many variation of the standard BL21 were therefore produced for different company:
BL21 --> standard strain for recombiant protein expression ( not suitable for vectors carryng t7 promoter, but for example you can use espression vectors carryng tac promoter or any other e.coli promoter (e.g pmal vectors or pcold vectors)
BL21(DE3) --> strain carryng the T7 polimerase and therefore suitable for recombinant expression of proteins clones in plasmids carryng the t7 promoter (eg. pet vectors).
n.b: From NEB you can find a version of this resistant to phage T1 and a version (named T7 express) where the T7 promoter where inserted in the genome with out the use of phage lambda (and therefore not named DE3 but also suitable for expression with T7 promoters)
BL21 plyss or BL21(DE3) plyss carryng the pLysS constitutively expresses low levels of T7 lysozyme, which reduces basal expression of recombinant genes by inhibiting basal levels of T7 RNA polymerase.
BL21 gold and BL21(DE3)gold modified to provide increased transformation efficiency and produce high-quality miniprep DNA.
Rosetta and Rosetta(DE3) that are BL21 derivatives carryng the pRARE plamid designed to codify for dna codons (e.g arginine rare codons) that are rarely codified in E.coli and therefore enanche the expresson of eukaryotic proteins or proteins derived for other bacteira with different codon usage respect e.coli.
Those are the most known BL21 derivate but broswing in the internet you can certanilly find some others and combination beetween them (e.g Rosetta plyss) with different names and properties.
good luck
Manuele
BL21 Gold cells, BL21 Gold(DE3) cells and BL21 Gold(DE3)pLysS cells are improved versions of BL21 competent cells. The BL21 Gold strains feature the Hte phenotype present in the highest efficiency Agilent competent cell strain, XL10-Gold. Therefore, BL21-Gold strains often provide increased transformation efficiency and produce high-quality miniprep DNA. They are also ideal for performing protein expression studies that utilize the T7 RNA polymerase promoter to direct high-level of protein expression.
Hi there,
BL21 Gold is an expression strain but it is not dedicated to T7 RNA polymerase driven transcription as it does not contain the DE3 genomic insertion encoding for the protein under the control of Plac. Using BL21 Gold for T7 driven expression imposes to infect the cells with CE6 phage. Whereas BL21 Gold(DE3) cells and BL21 Gold(DE3)pLysS are made for T7 driven expression induced by IPTG. For more details read the following:
https://cn.agilent.com/cs/library/usermanuals/public/230130.pdf
Dear Luckas
BL21 is a E.coli strain derived from E.coli type B strains (and not K-12 as happen for the most other strains suitable for cloning e.g DH5aplha). Characteristics such as protease deficiency (lon and ompT proteases), often regarded as common characteristics among B lineage, has driven the development of those strains for protein expression host.
Many variation of the standard BL21 were therefore produced for different company:
BL21 --> standard strain for recombiant protein expression ( not suitable for vectors carryng t7 promoter, but for example you can use espression vectors carryng tac promoter or any other e.coli promoter (e.g pmal vectors or pcold vectors)
BL21(DE3) --> strain carryng the T7 polimerase and therefore suitable for recombinant expression of proteins clones in plasmids carryng the t7 promoter (eg. pet vectors).
n.b: From NEB you can find a version of this resistant to phage T1 and a version (named T7 express) where the T7 promoter where inserted in the genome with out the use of phage lambda (and therefore not named DE3 but also suitable for expression with T7 promoters)
BL21 plyss or BL21(DE3) plyss carryng the pLysS constitutively expresses low levels of T7 lysozyme, which reduces basal expression of recombinant genes by inhibiting basal levels of T7 RNA polymerase.
BL21 gold and BL21(DE3)gold modified to provide increased transformation efficiency and produce high-quality miniprep DNA.
Rosetta and Rosetta(DE3) that are BL21 derivatives carryng the pRARE plamid designed to codify for dna codons (e.g arginine rare codons) that are rarely codified in E.coli and therefore enanche the expresson of eukaryotic proteins or proteins derived for other bacteira with different codon usage respect e.coli.
Those are the most known BL21 derivate but broswing in the internet you can certanilly find some others and combination beetween them (e.g Rosetta plyss) with different names and properties.
good luck
Manuele
BL21-Gold(DE3) competent cells are designed for easy induction and high-level protein expression.
The genotypes are on page 3:
https://www.agilent.com/cs/library/usermanuals/public/230130.pdf
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