flag tag - (Dec/11/2013 )

hi every body.

I come cross a gene with two different format one is gene +flag tag on N-terminus and the other is gene + flag tag on C-terminus.

I am wondering to know what is reason to have flag tag on C or N-terminus, and what's benefit of this sites.

I know that N-terminus is at begging of protein and C-terminus before stop codon of protein. 

is any one can help with this, thank u.

Its hard to predict on which terminus the protein should be tagged; however selecting a 'tag or the terminus' are by considering that the inclusion of tag should'nt interfere with the biological function or the properties of the protein.  

and exposed for selection (as when purifying) in the form you require (native or denatured).