Myc tags - (Feb/01/2011 )
As a biological chemist it is my understanding that the addition of protein tags to the N terminus of a protein alters folding and ultimately the shape of the protein when cloned through transfection. is this correct?
I have been asked to assess the topology of a protein which has no crystal structure. protein prediction programs return a model which differes in the number of transmembrane helices. the issue relates to the location of the N terminues (intra v's extra- cellular) and there is one article which dominates the proteins structure due to myc tagging of the N terminus. A myc tag itself is hydrophillic therefore this could potentially affect the ability for the N terminus thus to transect the membrane to be identified extracellularly.
any thoughts would be greatly appreciated.
Yes, tags can affect the structure and function of a protein. Could you tag the protein at both ends (i.e. one clone with N-terminal and another with C-terminal). It is best to use tags that are as small as possible (e.g. FLAG, HA) so as to disrupt the folding minimally.
If you have no crystal structure... are you trying to purify the protein and then do crystallography on it? If so, have a look into thrombin cleavage systems.