Temperature control in the T7 RNA polymerase/promoter system. (For protein expression)?

Zophonias O. Jonsson zjons at vetbio.unizh.ch
Wed Feb 26 10:31:16 EST 1997

In article <5f0jic$1ete$1 at snunews.snu.ac.kr>, newera at plaza.snu.ac.kr () wrote:

> Why is the temperature control for growing E. coli under the T7 RNA 
> polymerase/promoter system required?

  Generally one does not have to play around much with temperature when
expressing proteins using the T7 promoter system.  Sometimes one can
increase yields of soluble protein by inducing at low temperatures and
sometimes problems with toxicity can be alleviated, but in general growth
and induction at 30 or 37*C is sufficient for most proteins.
  The protocol you describe sounds like a special case.  You did not
mention what E.coli strain was used as host.  If it is a normal DE3
lysogen, where the T7 RNApol is controlled by a Lac promoter, this
temperature juggling is very strange.  If, on the other hand, the
expression strain contains the T7 pol under the control of a heat
inducible promoter (such as lambda PL in a strain with
temperature-inducible cI repressor), this wold make sense.  I have never
heard of such a beast, however.  If it exists it might be interesting !


Zophonias O. Jonsson
Institut fur Veterinarbiochemie               Tel: (41-1)-257-54-75
Universitat Zurich-Irchel                     Fax: (41-1)-362-05-01
Winterthurerstrasse 190
CH-8057 Zurich

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