In article <5f0jic$1ete$1 at snunews.snu.ac.kr>, newera at plaza.snu.ac.kr
writes
>Why is the temperature control for growing E. coli under the T7 RNA
>polymerase/promoter system required?
The induction of T7 RNA polymerase in this system is temperature
controlled. The T7 RNA pol is downstream of a lambda PL promoter which
in turn is controlled by a temperature sensitive cI repressor gene. the
heat shift from 30 to 42 inactivates the cI repressor, inducing
expression of the T7 pol. Once the T7 pol is produced it in turn
controls the overexpression of the gene down stream of the T7 promoter.
Lambda PL promoters and the cI857 expression system have been around for
years before the T7 expression system. It's just in this case onentrols
the other. In my hands this sometimes give better expression than
BL21(DE3) inducing the T7 RNA pol with IPTG.
Duncan
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The problem with being on the cutting edge is that you occasionally get
sliced from time to time....
Duncan Clark
DNAmp Ltd.
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http://www.dnamp.comhttp://www.genesys.demon.co.uk
