Chris,
Can you or others speculate, perhaps in light of the structure, why a
his-tag would cause precipitation?
Jacob Keller
***
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
Dallos Laboratory
F. Searle 1-240
2240
Hi Jorge,
using a system where you can cleave off the His-tag (with TEV, FactorX,
etc) adds a purification step which is complementary to the first
purification step (Ni-column etc). In my experience this results in very
pure protein which makes it more likely to crystallise.
Therefore I
Dear all,
Concerning the crystallization of proteins with a His-tag, based
upon discussions on this bulletin board and on the article
Mike Carson, David H. Johnson, Heather McDonald, Christie Brouillette
and Lawrence J. DeLucas, His-tag impact on structure, Acta Cryst. D63,
295-301, (2007).
Another theory is that trace amounts of Ni may leech off the column during
purification and coordinate with multiple His-tags on the pure protein,
causing them to aggregate.
For sure. We had a case where a protein would precipitate after post-Ni-NTA
dialysis. The precipitate would go back
Hi Jorge,
We have had cases both for and against leaving His-tags on proteins. In
one case, the presence of the His-tag was causing the protein to
precipitate, blocking our attempts at crystallization until we removed
it. However, we also had a different protein that crystallized
In our case, incubation in the presence of imidazole can knock the
protein out of solution- this was gleaned from crystallization
conditions containing imidazole. The best we could come up with is that
the imidazole groups from the His-tag were interacting with neighboring
protein in
