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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by careful investigation of the following parameters: dehydration rate, final relative humidity and total incubation time Tinc. Of these, the most important was shown to be Tinc. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.
Glypicans are multifunctional cell surface proteoglycans involved in several important cellular signalling pathways. Glypican-1 (Gpc1) is the predominant heparan sulphate (HS) proteoglycan in the developing and adult human brain. The two N-linked glycans and the C-terminal domain that attaches the core protein to the cell membrane are not resolved in the Gpc1 crystal structure. Therefore we have studied Gpc1 using crystallography, small-angle X-ray scattering and chromatographic approaches to elucidate the composition, structure and function of the N-glycans and the C-terminus, and also the topology of Gpc1 with respect to the membrane. The C-terminus is shown to be highly flexible in solution, but it orients the core protein transverse to the membrane, directing a surface evolutionarily conserved in Gpc1 orthologues towards the membrane, where it may interact with signalling molecules and/or membrane receptors on the cell surface, or even the enzymes involved in HS substitution in the Golgi apparatus Furthermore, the N-glycans are shown to extend the protein stability and lifetime by protection against proteolysis and aggregation.


Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration.,Awad W, Svensson Birkedal G, Thunnissen MM, Mani K, Logan DT Acta Crystallogr D Biol Crystallogr. 2013 Dec;69(Pt 12):2524-33. doi:, 10.1107/S0907444913025250. Epub 2013 Nov 19. PMID:24311593<ref>PMID:24311593</ref>
Structural aspects of N-glycosylations and the C-terminal region in human glypican-1.,Awad W, Adamczyk B, Ornros J, Karlsson NG, Mani K, Logan DT J Biol Chem. 2015 Jul 22. pii: jbc.M115.660878. PMID:26203194<ref>PMID:26203194</ref>


From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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