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Open AccessFeature PaperArticle

Lactose Binding Induces Opposing Dynamics Changes in Human Galectins Revealed by NMR-Based Hydrogen–Deuterium Exchange

1
Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan
2
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
3
Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan
*
Author to whom correspondence should be addressed.
Molecules 2017, 22(8), 1357; https://doi.org/10.3390/molecules22081357
Received: 26 July 2017 / Revised: 8 August 2017 / Accepted: 10 August 2017 / Published: 16 August 2017
(This article belongs to the Special Issue Recent Advances in Biomolecular NMR Spectroscopy)
Galectins are β-galactoside-binding proteins implicated in a myriad of biological functions. Despite their highly conserved carbohydrate binding motifs with essentially identical structures, their affinities for lactose, a common galectin inhibitor, vary significantly. Here, we aimed to examine the molecular basis of differential lactose affinities amongst galectins using solution-based techniques. Consistent dissociation constants of lactose binding were derived from nuclear magnetic resonance (NMR) spectroscopy, intrinsic tryptophan fluorescence, isothermal titration calorimetry and bio-layer interferometry for human galectin-1 (hGal1), galectin-7 (hGal7), and the N-terminal and C-terminal domains of galectin-8 (hGal8NTD and hGal8CTD, respectively). Furthermore, the dissociation rates of lactose binding were extracted from NMR lineshape analyses. Structural mapping of chemical shift perturbations revealed long-range perturbations upon lactose binding for hGal1 and hGal8NTD. We further demonstrated using the NMR-based hydrogen–deuterium exchange (HDX) that lactose binding increases the exchange rates of residues located on the opposite side of the ligand-binding pocket for hGal1 and hGal8NTD, indicative of allostery. Additionally, lactose binding induces significant stabilisation of hGal8CTD across the entire domain. Our results suggested that lactose binding reduced the internal dynamics of hGal8CTD on a very slow timescale (minutes and slower) at the expense of reduced binding affinity due to the unfavourable loss of conformational entropy. View Full-Text
Keywords: galectins; protein dynamics; NMR spectroscopy; ligand binding galectins; protein dynamics; NMR spectroscopy; ligand binding
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Chien, C.-T.H.; Ho, M.-R.; Lin, C.-H.; Hsu, S.-T.D. Lactose Binding Induces Opposing Dynamics Changes in Human Galectins Revealed by NMR-Based Hydrogen–Deuterium Exchange. Molecules 2017, 22, 1357.

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