Dear all,
I need to plan some over expression experiments for which I need to constract several Chaperones containing plasmeds.
I look extensivly in the literature and couldnt find out the reson for choosing one kind of tag or another, I.e. 3HA, 6-His, Flag.
Someone have any idea why one chooses one kind of tag and not the other.
Usualy I would use something that was already used and established, in the way that it dose not interfere with the action of the protein. But the question stays why one choose one and not the other?
Guy

Most people seems to choose a tag somewhat randomly (it's familiar, I have the plasmid, etc.) rather than for any scientific reason. There are some good reasons to choose (or not choose) a particular tag.

His and FLAG tags are quite small and considered as less likely to interfere with protein folding and function.

GST dimerizes, forcing your tagged protein into dimers.

FLAG and GST tags have good antibodies against them - anti-His antibodies are somewhat dubious.

FLAG is expensive to work with (Sigma patent = price gouging).

Hs-tag is easy and inexpensive to purify on nickel columns. The purity is not as good as with other tags, although the purity can be improved using a cobalt agarsoe support instead of nickel for purification.