Epitope tag positioning - (Oct/06/2006 )

Does an epitope tag like c-myc or his have to be on the N- or C- terminus to be recognized by an antibody? Or can the tag be located anywhere within the protein of interest?

Usually you buy a vector that has everything set up for you to clone in your cDNA to either the N or C terminus, just for convenience. I would think people would avoid putting it in the middle of the protein so as not to disrupt the folding and hence 3D structure of the protein. Also, the tag may not be solvent accessible if you place it in the middle of the protein. This may not be a problem for westerns but may stop your Ab from working in FACS or other assays where the proteins aren't denatured.

Hope this helps,
Moutainman

I am actually engineering a protein (vector) and plan to put my tag in a region that I am fairly sure will not disrupt folding and is located on the outside of the protein where it should be solvent accessible. The question is will an antibody bind if the epitope is not near/in an end terminus?

depends on the protein.

most secreted proteins have tag at the C terminus, as they might undergo cleavage.

having a tag within the protien is risky but people have done this before.