ABSTRACT
The specific recognition of carbohydrates by lectins plays a major role in many cellular processes. Galectin-1 belongs to a family of 15 structurally related beta-galactoside binding proteins that are able to control a variety of cellular events, including cell cycle regulation, adhesion, proliferation, and apoptosis. The three-dimensional structure of galectin-1 has been solved by x-ray crystallography in the free form and in complex with various carbohydrate ligands. In this work, we used a combination of two-dimensional NMR titration experiments and molecular-dynamics simulations with explicit solvent to study the mode of interaction between human galectin-1 and five galactose-containing ligands. Isothermal titration calorimetry measurements were performed to determine their affinities for galectin-1. The contribution of the different hexopyranose units in the protein-carbohydrate interaction was given particular consideration. Although the galactose moiety of each oligosaccharide is necessary for binding, it is not sufficient by itself. The nature of both the reducing sugar in the disaccharide and the interglycosidic linkage play essential roles in the binding to human galectin-1.
Subject(s)
Galectin 1/chemistry , Galectin 1/metabolism , Molecular Dynamics Simulation , Nuclear Magnetic Resonance, Biomolecular , Oligosaccharides/chemistry , Oligosaccharides/metabolism , Calorimetry , Disaccharides/chemistry , Disaccharides/metabolism , Galactose/chemistry , Galactose/metabolism , Glycosides/chemistry , Humans , Hydrogen Bonding , Ligands , Molecular Conformation , Protein Binding , Protein Stability , Software , Thermodynamics , Water/chemistryABSTRACT
Galectins belong to the family of glycan-binding proteins, defined by at least one conserved carbohydrate-recognition domain with a highly conserved amino acid sequence and affinity for beta galactosides. They all possess a tryptophan residue in the carbohydrate binding site that forms hydrophobic contacts with the carbohydrate ligands. Site directed mutagenesis experiments have shown that this conserved aromatic residue plays a key role in the interaction. We have studied the interaction between the corresponding human Galectin-1 in silico mutants and different carbohydrate ligands using molecular dynamics in explicit solvent. The results confirm the importance of the conserved tryptophan residue in the affinity of the ligand and gives further insights into the mode of interaction between lactose derivatives and human Galectin-1.