I found that several expression constructs of published protein structures containing an N-teiminal fusion tag GAMGSGIQRPTST. What's the founction of this fusion tag?
I did a BLAST search on this amino acid sequence and found 11 exact matches from unrelated protein sequences. In no case was the function of the sequence annotated. This suggests that it is a sequence arising from a cloning vector that is not intended to be translated, and is not meant to be part of the proteins (a mistake, in other words). Do you have the nucleotide sequence?
Adam B Shapiro Thank you for your reply! I re-checked the sequence of the vector and found that it was a translation product of the multiple cloning sites of a modified pFastBac vector. Thanks again! :)
Update:
It's great to hear that you were able to identify the origin of the fusion tag. The multiple cloning site (MCS) in vectors like pFastBac is often included to facilitate the insertion of various DNA fragments, and sometimes these sites can get translated into short peptide sequences if they are not properly removed or if they are included intentionally for some purpose.
Protein Guidance:
1-The tag acts as a directional signal to enter the protein into the endoplasmic reticulum or across cell membranes. 2-The cellular machinery responsible for transporting the protein recognizes this tag.
3-Ensuring the fusion process: The tag helps push the protein to penetrate the cell membrane or endoplasmic reticulum in the correct manner, ensuring its fusion with the membrane.
4-Maintaining the tertiary structure of the protein: The tag maintains the tertiary structure of the protein during the fusion process, ensuring the integrity of the final shape of the protein.
5-Targeting the protein to the appropriate location: The tag directs the protein to the appropriate location within the cell, whether the plasma membrane or other internal organelles.
In general, the N-terminal fusion tag GAMGSGIQRPTST plays a fundamental role in ensuring the transport of proteins across membranes.
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