Why bl-21 use as protein exression strain?

Chris McDermott-Roe via methods%40net.bio.net (by cjmcdermottroe from googlemail.com)
Tue Mar 15 05:58:53 EST 2011

If I remember correctly, standard cloning strains (top10s etc) dont carry T7
and thus cant express your cloned gene.  BL21s allow for inducible protein
expression.  Certain proteins are toxic and so suppression is important.  I
use BL21(DE3)pLysS cells, which produce T7 lysozyme from their pLysS
plasmid; this prevents (so the companies say but actually it just lowers)
expression of your gene of interest.  Then you hit them with IPTG to induce
expression.  Like I said, in my hands, the T7 lys-induced repression is not
great and if your protein is even moderately toxic, I tighter system (such
as virus-mediated T7 expression) may be necessary.

On 14 March 2011 22:54, sudheer babu <sudheer.pbm07 from gmail.com> wrote:

> Hi people
> Can anyone please tell me why Bl-21 use as Protein expression strain?
> --
> Sudheer Babu.S
> ITC student
> Institute of Biochemistry
> Biological Research Center
> Szeged,Hungary.
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