If there was a very strong RBS site placed between the promoter and the AUG of the fusion partner at the N terminal, while there would also be the Shine-Dalgarno sequence placed in between the protein of interest and that N-terminal fusion partner. What effect would that have on the expression? would you expect to see a heterogenous protein expression where there would be some full length fusion protein expressed, as well as some expression of the protein of interest without the fusion partner?
Can you make a drawing or some sort of scheme? Just sketch something on a piece of paper and take a picture with your phone...
Assuming the protein of interest has the normal start codon appropriately placed after the shine dalgarno, then I would expect you would get expression of both forms, the fusion protein as well as the protein of interest alone. I'm not sure whether it would be at the same level as it would without the upstream fusion partner, but I would expect ample expression none the less.
Assuming that the coding sequences of the fusion partner and the protein of interest are fused together (that is, they are both in frame and there are no in-frame stop codons between them) and that the second RBS has a properly spaced ATG or GTG codon downstream then yes, you will have some translation off ribosomes binding directly to the second RBS. If there is no suitable start codon downstream you will get some translational pausing, as illustrated here:
Article The anti-Shine-Dalgarno sequence drives translational pausin...
Hope it helps!
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