Conformational selection in glycomimetics: human galectin-1 only recognizes syn-Ψ-type conformations of β-1,3-linked lactose and its C-glycosyl derivative.

The human lectin galectin-1 (hGal-1) translates sugar signals, that is, β-galactosides, into effects on the level of cells, for example, growth regulation, and has become a model for studying binding of biopharmaceutically relevant derivatives. Bound-state conformations of Galβ-C-(1→3)-Glcβ-OMe (1) and its βGal-(1→3)-βGlc-OMe disaccharide parent compound were studied by using NMR spectroscopy (transferred (TR)-NOESY data), assisted by docking experiments and molecular dynamics (MD) simulations. The molecular recognition process involves a conformational selection event. Although free C-glycoside access four distinct conformers in solution, hGal-1 recognizes shape of a local minimum of compound 1, the syn-Φ/syn-Ψ conformer, not the structure at global minimum. MD simulations were run to explain, in structural terms, the observed geometry of the complex.