BL21(DE3) and trc promoter

Petri Kursula pkursula at
Wed Feb 9 02:57:14 EST 2000

> BTW, the (DE3) bit of your BL21(DE3) is unncessary for pTrc99a.  If you are
> confused by the strains, all you need to know is that there are cloning
> strains and there are expression strains.  Bl21 is an expression strains.

Does the DE3 actually interfere with the expression from a trc promoter? I
just have it in those cells because someone forgot to write the DE3 in the
tubes...would the simultaneous expression of the T7 polymerase from the
lac promoter affect my yield?

Another question is: I have seen reports of protein expression in the DH5a
strain. Is this a cell line suitable for expression in general, or does it
have a bunch of nasty proteases?

Petri Kursula           "I am somehow less interested in the weight and
University of Oulu    convolutions of Einstein's brain than in the near
Petri.Kursula at  certainty that people of equal talent have lived          and died in cotton fields and sweatshops."                        -- Stephen Jay Gould 

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