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Constitutive Fusion Protein Expression in BL21(DE3) Cells

Dima Klenchin klenchin at macc.wisc.edu
Tue Mar 5 10:58:34 EST 1996

In article <biotech-0403961716060001 at cyto.cytosignal.com>,
   biotech at ni.net (David J Benz) wrote:
->Hello Everyone! We're having some trouble with our protein expression
->system. Like almost everyone else, we use an expression vector to express
->a His-Tagged fusion protein, which we subsequently purify over a Qiagen
->Ni-NTA column. What we've noticed is that lately our proteins are
->beginning to show up in uninduced bacteria. The tac promoter is supposed
->to drive transcription, and shouldn't be active in the absence of IPTG.
->Why are our proteins expressing in uninduced bacteria?

I have exactly the samr with GST fusions (pGEX-2T in JM109). Up
to the point where in dense culture there is no difference
between induced nad uninduced cultures. Would really love
to know how I can prevent this. Please, if you get any useful info,
post summary or email copy to me. 


- Dima


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