microheterogeneity and tagged proteins

[Cornelius Krasel]

Alan H. Schulman (schulman at convex.operoni.helsinki.fi) wrote:
: I would like to express a protein in E. coli for ultimate crystallization.
: It would be convenient to express it as a fusion protein.  Of the several
: systems available (6xHis (InVitroGen), strep-tag (Biometra),clip (Promega)
: etc., does anyone have experience with the result in crstallization?  How
: cleanly can the tag be cleaved off, without generating heterogeneity from
: multiple cleavage positions?

When I was a student, I once worked with antibody fragments expressed in
the periplasm of E. coli and tagged with a self-made his-tag. This tag
wasn't cleaved off at all and apparently did not interfere with
crystallization. Of course, you probably can't generalize from this
experience :-)

--Cornelius.

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