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46 bp shift in start codon ? - tac promoter in pMAL is different from journal (Nov/06/2006 )

Oh dear,

I just find that NEB is poor, the gene map they provide contain nothing.
The vector pMAL-c2x have a tac promoter, but they don't tell us where is RBS and where is transcription start.

Finally, I find the first paper about tac promoter in PNAS, and it tell that start codon appear 21 bp downstream from the lac operator.

However, the first ATG is 67 bp after the lac operator in pMAL. Do you know what NEB done on this vector ?

thx a lot laugh.gif


The mRNA often contains a 5' untranslated region (5' UTR). There is no requirement that the RBS and ATG occur at a specific spot relative to the transcription start. The RBS is typically 6-10 bp before the ATG, and has a consensus sequence AGGAGG.
Here, the RBS is around 1512-1518 in the NEB sequence.