expression with BL21(DE3)

Frank O. Fackelmayer fof1 at
Thu Nov 6 06:16:25 EST 1997

In article <v03020901b086766d1222@[]>,
moffatt at SCIBORG.UWATERLOO.CA (Barbara Moffatt) wrote:

> Hello:
> I have a colleague that wishes to transform a plasmid library created from
> that Stratagene lambda zap (unizap) vector into BL21(DE3) for expression
> from the T7 promoter. Can anyone comment on the expression levels from a
> non pET vector, using a BL21(DE3) host? Novagen says they don't guarantee
> it and I only have experience using pET vectors with this host.
> Thanks in advance for your assistance.
> Barb Moffatt
> moffatt at

Hi Barb,
There seems to be no problem in using other T7-vectors than pET. We
routinely use pRSET expression vectors, with good results. Expression from
pBluescript also works (that´s your system, I suppose), but does not give
high yields. It depends on what you want to do with your protein: For
screening a library it is sufficient, but it´s not that good for
I agree with Armin that BL21 are hard to transform. I really wouldn´t do
that with a library...

Hope this helps.

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