Conformations, dynamics and interactions of di-, tri- and pentamannoside with mannose binding lectin: a molecular dynamics study

The binding of serum mannose-binding protein A (MBP-A) to high mannose N-linked glycoproteins, present on the surface of microorganism, activates the complement system. It is very important to explore the overall conformations of these ligands in the binding site of the MBP-A, which is very much dependent on the conformation of the manno-di-, tri- and the penta-saccharides that represent the component structures of these high-mannose type oligosaccharides. Herein, we report the possible conformations of α-(1→6)-linked dimannoside, benzyl-substituted trimannoside and core pentamannoside of the N-linked glycan in the binding site of MBP-A, with the help of molecular dynamics simulations. The results indicate that for all three ligands in addition to the non-reducing terminal mannose moiety the reducing moieties also interact with protein. Binding free energy calculations also indicate that the benzyl-substituted trisaccharide has higher affinity in comparison to the methyl substituted one. We have also found some conformers of the pentasaccharide, which have higher binding affinity than the monosaccharide.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Elucidation of bound conformations of di-, tri- and pentamannoside ligands in MBP-A binding site. ► Calculation of binding free energy from changes in solvent accessible surface area of the complexes. ► Determination of alternative/ different mode of binding between the ligands and the lectin.