I was reading a paper that used escherichia coli origami DE3 strains to express a certain protein and the vector used was a pTrcHis-Topo with a trc promoter. I am wondering if they made use of the chromosomal copy of T7 RNA polymerase gene present in this strain or not because as far as I understand T7 rna polymerase needs a T7 promoter.
Most likely, their gene got expressed using the E. coli polymerase and the T7 polymerase was of no use. Maybe they use the origami DE3 host because they had no other host carrying the the origami ( gor-trx) genotype to foster proper formation of disulfide bridges.
I concur with Pierre Béguin that the Trc promoter is not recognized by T7 polymerase but they may have selected this strain for the "origami" phenotype.
Hi there,
I fully agree with Pierre and Michael. The IPTG used for induction will relieve the downregulation of the trc promoter by LacI (operator sequences of the lac promoter are present in trc promoter) and bacterial polymerase will be able to initiate efficient transcription. T7 RNA polymerase is strictly specific of T7 promoter sequence.
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