T7 Promoters and exp

[Lauri Lintott]

> 
> Hi, Netters!
>   > difficulties with T7 promoters?  I am surprised, but I am not exactly the
> most experienced individual with protein expression.  Does anyone have any
> suggestions for ways to suppress the background expression in our uninduced
> cells?  We have tried using JM109 and XL-1 Blue cells - similar problems in
> either line.  Thanks for any help/commiseration.  Laura Moen  Email or post
> is OK.  Email address: LKM100F at ODUVM.cc.odu.edu  (U.S.)
> 
> 
I have experiance similar problems with a pET vector.  I found
that using sorbitol medium (J.R. Blackwell and R. Horgan, 1991,
FEBS Lett 295:10-12) supressed any uninduced expression, although
it did not seem to effect the induced level.  The media is LB +
1M sorbitol and 2.5 mM betaine (filter sterilize 1 M betaine 
and add to LB/sorbitol after it has cooled).

Hope this helps
Lauri Lintott
Bio. Sci. U of Calgary