On Tue, 27 Mar 2001 01:16:48 +0100, ChenHA <hzhen at freeuk.com> wrote:
>.....that they have been able to crystallise some proteins only when the
>his tag is present. From what I was told, it would appeared that the
>his tag helped to make the protein mono-disperse in solution.
Well, so u can consider the problem from a reverse point of view; that
is: keep the HisTag only if u think it is improving some protein
feature(e.g. solubility or stability). About the state of aggregation
in solotion u can check it by DLS of His-tagged and Non-His-Tagged
protein.
>This of course doesn't mean that all proteins may benefit from having
>a his tag in their crystallisation, just that some (I stress some)
>may.
I agree with you about *some*. Any additional non-structurated amino
acid sequence (i.e. the HisTag) in a protein will probably decrease
the chance of get crystals of it. Obviously this don't mean u'll never
crystallize it; it's only a matter of probability.
The fact that in His-tagged-protein 3D structure the His-Tag itself is
not visible means that it isn't structurated, so it doesn't contribute
in crystal conctacts and eventually it doesn't contribute to stabilize
it (the crystal).
Bye, Gianluca
gianluca.molla at uninsubria.it
