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 dis coideum has been modelled from the X-ray coordinates of the monocot mannose -binding lectin from snowdrop (Galanthus nivalis). Docking experiments perf ormed on the three-dimensional model showed that two of the three mannose-b inding sites of the comitin monomer are functional. They are located at bot h 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 c omitin which is believed to link the Golgi vesicles exhibiting mannosylated membrane glycans to the actin cytoskeleton in the cell.