Umar,
Check out: Czepas et al. The impact of Lys-->Arg surface mutations on
the crystallization of of the globular domain of RhoGDI, Acta D (2004)
60 275-280. They point out that sulfate ions can help mediate contacts
between arginine residues from neighboring molecules in the crystal.
You may have already considered the surface entropy server
(http://nihserver.mbi.ucla.edu/SER/) to help identify any specific
stretches of amino acids that could be mutated to reduce entropy and
possibly promote crystallization. Maybe there are a couple regions of
your sequence that are flagged as particularly unfavorable in terms of
their predicted entropy contribution. There is evidence that lysine is
more of a problem in this respect as compared to arginine (Derewenda et
al. Acta D (2006) 62 116-124).
Good luck,
-Andy
===========================================
Andrew T. Torelli Ph.D.
Postdoctoral Associate
Department of Chemistry & Chemical Biology
Baker Laboratory, Cornell University
Ithaca, NY 14853
===========================================
On 11/2/2009 8:39 AM, Jan Rash wrote:
Dear All,
I have a question regarding the crystallization of lysine and arginine
rich protein around 13%. So far our attempts to crystallize this protein
have not been successful although the secondary structure predictions,
CD spectroscopy measurements clearly show that this protein is folded. I
presume that these lysine and arginine are the sources of the local
flexibility in the protein even though the protein is globular overall.
Moreover, my attempts to crystallize the limited proteolysis fragments
also did not achieve crystals. I have also tried the crystallization
with its binding partners and could not succeed. I think any compound
that binds to the lysine/arginine side chains might affect the
crystallization process thereby reducing the internal flexibility of
protein. Can anybody suggest some effective strategy for the
crystallization?
Thanks
Umar
