As I understand, the only difference between them is that pET14b contains the T7 promoter whereas in pET15b T7 promoter plus lac operator. I read that T7/lac increases the chance of expression of a recombinant protein if it is highly toxic to BL21(DE3) hosts. I want to express GAPDH (Glyceraldehyde 3-phosphate dehydrogenase) in E. coli BL21(DE3). Should it be toxic and imply a gain in expression if I go from pET14b to pET15b?
Thanks,
Sheila
GAPDH should not be toxic in E. coli so I don't think there would be any advantage in going from pET14b to pET15b in your case. There should be tighter regulation with pET15b so the basal level of expression should be lower and you are likely to see an increased ration of uninduced to induced, but that is because the unindexed levels will be lower. The induced levels should be comparable.
So if you are doing physiological experiments this might be an advantage, but if you are just expressing protein then it won't be important.
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