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Double Affinity Amplification of Galectin–Ligand Interactions through Arginine–Arene Interactions: Synthetic, Thermodynamic, and Computational Studies with Aromatic Diamido Thiodigalactosides
Author(s) -
Cumpstey Ian,
Salomonsson Emma,
Sundin Anders,
Leffler Hakon,
Nilsson Ulf J.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701932
Subject(s) - chemistry , arginine , galectin , stereochemistry , isothermal microcalorimetry , ligand (biochemistry) , biochemistry , amino acid , thermodynamics , enthalpy , physics , receptor
A series of aromatic mono‐ or diamido‐thiodigalactoside derivatives were synthesized and studied as ligands for galectin‐1, ‐3, ‐7, ‐8N terminal domain, and ‐9N terminal domain. The affinity determination in vitro with competitive fluorescence‐polarization experiments and thermodynamic analysis by isothermal microcalorimetry provided a coherent picture of structural requirements for arginine–arene interactions in galectin–ligand binding. Computational studies were employed to explain binding preferences for the different galectins. Galectin‐3 formed two almost ideal arene–arginine stacking interactions according to computer modeling and also had the highest affinity for the diamido‐thiodigalactosides ( K d below 50 n M ). Site‐directed mutagenesis of galectin‐3 arginines involved in binding corroborated the importance of their interaction with the aromatic diamido‐thiodigalactosides. Furthermore, the arginine mutants revealed distinct differences between free, flexible, and solvent‐exposed arginine side chains and tightly ion‐paired arginine side chains in interactions with aromatic systems.