protein activity with extra N-terminal peptide

Trond Erik Vee Aune trondaun at
Sat Apr 29 02:32:09 EST 2006

Isaac Li wrote:

> Hi,
> I have a expression vector based on the pTriX1.0 vector.
> the vector was constructed with three cut sites (Nco, Spe, BamH) in 
> front of the protein to be expressed, which results in expression with 
> the few extra residues before the real start codon of the protein:
> M G L T S G S - [M ... actualy protein sequence]
> would this be a problem to affect the activities of the protein i am 
> expressing?

It really depends on the protein and it's overall function/structure. 
Some proteins have no problem coping with a few extra residues, others 
would not function properly.

> do general expressing vectors have extra residues before the actual 
> protein?

Generally one aims to clone the gene of interest into the first ATG 
downstream of the translation initiation region.

That said, many commercial vectors contain different N-terminal fusion 
partners to achieve effecient translocation, expression, isolation, etc.

Trond Erik

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