Glycobiology Advance Access published online on October 23, 2006
Glycobiology, doi:10.1093/glycob/cwl062
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1 Glyco-Immunochemistry Research Laboratory, Institute of Molecular and Cellular Biology, College of Medicine, Chang-Gung University, Kwei-san, Tao-yuan 333, Taiwan
* To whom correspondence should be addressed. Gene duplication and sequence divergence are driving forces toward establishing protein families. To examine how sequence changes affect carbohydrate specificity the two closely related proto-type chicken galectins CG-14 and CG-16 were selected as models. Binding properties were analyzed using a highly sensitive solid-phase assay. We tested 56 free saccharides and 34 well-defined glycoproteins. The two galectins share preference for the II vs. I version of
Received June 20, 2006
Revised September 18, 2006
Accepted October 15, 2006
Article
Activity-structure correlations in divergent lectin-evolution: fine specificity of chicken galectin CG-14 and computational analysis of flexible ligand docking for CG-14 and the closely related CG-16
Albert M. Wu 1 *, Tanuja Singh 1, Jia-Hau Liu 1, Mickael Krzeminski 2, Roland Russwurm 3, Hans-Christian Siebert 3, Alexandre M.J.J. Bonvin 2, Sabine André 3, and Hans-Joachim Gabius 3
2 Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
3 Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians- University, Veterinärstr. 13, 80539 Munich, Germany
Albert M. Wu, E-mail: amwu{at}mail.cgu.edu.tw
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Abstract
-galactosides. A pronounced difference is found due to the reactivity of CG-14 with histo-blood group ABH active oligosaccharides and A/B active glycoproteins. These experimental results prompted to determine activity-structure correlations by modeling. Computational analysis included consideration of flexibility of binding partners and presence of water molecules. It provided a comparative description of complete carbohydrate recognition domains, which had so far not been characterized in animal galectins. The structural models assigned II, I selectivity to a region downstream of the central Trp moiety. Docking revealed that the tetrasaccharides can be accommodated in their free-state lowenergy conformations. CG-14's preference for A vs. B epitopes could be attributed to a contact between His124 and the N-acetyl group of GalNAc. Regarding inter-galectin comparison, the Ala53/Cys51 exchange affects the interaction potential of His54/His52. Close inspection of simulated dynamic interplay revealed reorientation of His124 at the site of the His124/Glu123 substitution with potential impact on ligand dissociation. In summary, this study identifies activity differences and provides information on their relation to structural divergence, epitomizing the value of this combined approach beyond galectins.![]()
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