We have crystallized a cyanobacterial phycoerythrin which having two (alpha
subunit) in an assymetric unit and held together by only three hydrogen bonds.
When we compare the A and B molecule the RMSD is 1.32. because they same
sequences then how it is possible to that two molecules are deviated at such
extent. now the question is are both the molecules are crystallographic dimer?
are two molecules are structural subunit as alpha 1 and alpha2?
Is there any problem in refinement ? The structure was refined at 2.6 A with
R 0.23/0.28
it sounds as if you have refined the structure without restraining the NCS. at
2.6A you would have to justify that (typically by showing that you get a
considerably lower Rfree without restraints than you do with restraints).
see these papers from the last millennium:
- G J Kleywegt & T A Jones, "Where freedom is given, liberties are taken",
Structure, 3, 535-540 (1995).
- G J Kleywegt, "Use of non-crystallographic symmetry in protein structure
refinement", Acta Crystallographica, D52, 842-857 (1996).
- G J Kleywegt & A T Brunger, "Checking your imagination: applications of the
free R value", Structure, 4, 897-904 (1996).
- G J Kleywegt & T A Jones, "Model-building and refinement practice", Methods
in Enzymology, 277, 208-230 (1997).
- G J Kleywegt, "Experimental assessment of differences between related
protein crystal structures", Acta Crystallographica, D55, 1878-1884 (1999).
- G J Kleywegt, "Validation of protein crystal structures" (Topical review),
Acta Crystallographica, D56, 249-265 (2000).
reprints available from http://xray.bmc.uu.se/gerard/citation.html
--dvd
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Gerard J. Kleywegt
[Research Fellow of the Royal Swedish Academy of Sciences]
Dept. of Cell & Molecular Biology University of Uppsala
Biomedical Centre Box 596
SE-751 24 Uppsala SWEDEN
http://xray.bmc.uu.se/gerard/ mailto:[EMAIL PROTECTED]
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