Homology modelling of the core domain of the endogenous lectin comitin: structural basis for its mannose-binding specificity

The N-terminal core domain of comitin from the slime mold Dictyostelium discoideum has been modelled from the X-ray coordinates of the monocot mannose-binding lectin from snowdrop (Galanthus nivalis). Docking experiments performed on the three-dimensional model showed that two of the three mannose-binding sites of the comitin monomer are functional. They are located at both ends of the comitin dimer whereas the actin-interacting region occurs in the central hinge region where both monomers are non covalently associated. This distribution is fully consistent with the bifunctional character of comitin which is believed to link the Golgi vesicles exhibiting mannosylated membrane glycans to the actin cytoskeleton in the cell.