Hi, I want to express three genes in E. coli. I have seen some papers which used inducible promoters, like IPTG promoter or Arabinose promoter, to express their genes heterologously. But, I have three genes. If I add one same inducible promoter to three genes, I think it's terrible. So I'm wondering that whether I can use different consitutive promoters to express these genes. Or maybe I can use two constitutive promoters to express two genes and use one inducible promoter to express one gene. Do you have some more reasonable suggestions?
The answer will very much depend upon the experiment. If you need all 3 proteins expressed at a similar ratio and all at the same time, then you can use either constitutive or inducible. In fact the easiest thing would be to make an operon of the 3 proteins and just use a single promoter to express all 3 concurrently. However if you want to differentially express them (say 2 proteins at one time and a 3rd at a different time) then you would need different promoters that can be induced independently. If there are any concerns regarding toxicity or you are striving for very high level expression you would be better off with inducible systems so you can make constructs and manipulate your strains without the stress of expression. However if toxicity is not an issue then either constitutive or inducible should be fine.
Michael J. Benedik Many thanks to your answer. I have one more question. How can I make an operon of 3 proteins?
You just clone the 3 genes in order after the promoter, but each should have its own ribosome binding site. keep the space between the genes short 10-20 nts)
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