---- Original message ----
>Date: Wed, 27 Jun 2012 10:14:58 -0400
>From: CCP4 bulletin board <
[log in to unmask]> (on behalf of "R. M. Garavito" <
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>Subject: Re: [ccp4bb] The effect of His-tag location on crystallization
>To:
[log in to unmask] >
> Most of the comments you will get will be anecdotal
> in that people will report the successful results
> and do not take the time or effort to characterize
> the less successful results. This often occurs
> because the tagged portion of the protein is most
> often disordered, even in the best crystals. Thus,
> other than saying "tagging on this end works, but
> tagging on that end doesn't," there is little more
> you can say. Each case will be different, and it is
> almost impossible to arrive at any generalized
> conclusion.
> We prefer C-terminal tagged proteins for a number of
> reasons, but if an N-terminally tagged protein
> crystallizes well, so be it. Of the dozens of N-
> and C-tagged protein structures we have solved in my
> lab and with collaborators, I have only seen one
> case of an ordered His-tag: the His residues had
> coordinated Cd ions, which proved essential for
> getting good crystals. However, beyond that there
> was not much more to say.
> For your protein and the resulting crystals, an
> N-terminally tagged protein crystallized well.
> Whether you can draw any more conclusions from
> these results depends on characterizing crystals of
> both N- and C-tagged proteins. Just assuming that
> the C-tagged protein is trying to crystallize in the
> same or related crystal form as the N-tagged protein
> is an unwarranted assumption without experimental
> evidence to back it up. That is why most groups
> just run with the winner.
> Cheers,
> Michael
> ****************************************************************
> R. Michael Garavito, Ph.D.
> Professor of Biochemistry & Molecular Biology
> 603 Wilson Rd., Rm. 513
> Michigan State University
> East Lansing, MI 48824-1319
> Office:
(517) 355-9724 Lab:
(517) 353-9125 > FAX:
(517) 353-9334 > Email:
[log in to unmask] > ****************************************************************
> On Jun 26, 2012, at 9:06 PM, weliu wrote:
>
> Dear all,
>
> We crystallized a protein and found that crystal
> quality greatly depended on the location of
> His-tag. When a His-tag was added at the
> C-terminus, only crystalline precipitate or
> spherical quasi crystals were grown. However, when
> the His-tag was moved to the N-terminus, single
> crystals were grown under a number of conditions,
> and the best one diffracted to 1.7 angstrom after
> optimization. I was wondering if there were
> published reports describing similar cases.
>
> Thank you in advance
>
> Wei Liu
