2qvw
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(New page: 200px<br /><applet load="2qvw" size="350" color="white" frame="true" align="right" spinBox="true" caption="2qvw, resolution 3.000Å" /> '''Structure of Giardi...)
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Revision as of 11:30, 23 January 2008
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Structure of Giardia Dicer refined against twinned data
Overview
The crystal structure of the enzyme Dicer from Giardia intestinalis was, solved to 3.3 A resolution by MAD using crystals belonging to space group, P2(1)2(1)2 [Macrae et al. (2006), Science, 311, 195-198]. These crystals, were derived from crystals that diffracted X-rays to 3.0 A resolution but, were refractory to structure determination because they were twinned. It, is shown here that the original Dicer crystals represent an unusual case, of perfect pseudo-merohedral twinning of orthorhombic crystals. Before the, twinning problem was overcome, it was possible to calculate a, low-resolution electron-density map in space group P4(1) that was used to, build a partial molecular model. Experimental phases were sufficient to, identify heavy-atom sites that indicated space-group inconsistency, leading to identification of the true space group. This information guided, the search for different crystallization conditions that yielded untwinned, crystals and ultimately a fully interpretable electron-density map.
About this Structure
2QVW is a Single protein structure of sequence from Giardia intestinalis with as ligand. Active as Ribonuclease III, with EC number 3.1.26.3 Full crystallographic information is available from OCA.
Reference
An unusual case of pseudo-merohedral twinning in orthorhombic crystals of Dicer., Macrae IJ, Doudna JA, Acta Crystallogr D Biol Crystallogr. 2007 Sep;63(Pt 9):993-9. Epub 2007, Aug 17. PMID:17704568
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