Double affinity amplification of galectin-ligand interactions through arginine-arene interactions: synthetic, thermodynamic, and computational studies with aromatic diamido thiodigalactosides.
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 nM). 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.
Cumpstey
Ian
I
Organic Chemistry, Lund University, POB 124, 22100 Lund, Sweden.
Salomonsson
Emma
E
Sundin
Anders
A
Leffler
Hakon
H
Nilsson
Ulf J
UJ
D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry* / Q000378:metabolism; D003958:Diamide / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D037161:Galectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D013865:Thioglycosides / Q000138:chemical synthesis / Q000737:chemistry*
D037161:Galectins; D006841:Hydrocarbons, Aromatic; D008024:Ligands; D020033:Protein Isoforms; D013865:Thioglycosides; D003958:Diamide; D001120:Arginine