Strong, Non-specific Adhesion Using C-Lectin Heterotrimers in a Molluscan Defensive Secretion

The defensive mucus produced by the slug Arion subfuscus is tough and remarkably sticky. It spreads rapidly and adheres strongly to a wide range of surfaces. The adhesion is equally strong on wettable (glass) and non-wettable (plastic) surfaces. The adhesion appears to depend on a group of proteins that adsorb equally well to a wide range of different natural and artificial surfaces. Prominent among these proteins were those that distinguish the adhesive secretion from the non-adhesive mucus. The adhesive proteins were not washed off by non-ionic detergent. Similarly, the adhesion of the glue as a whole was not affected by this treatment. In contrast, high salt concentrations washed the most abundant adhesive proteins off the surfaces, and correspondingly weakened the glue's attachment. The most abundant of the adhesive proteins were C-lectins, which appear to form heterotrimers. These and other lectin-like proteins in slug glue have a high proportion of aromatic amino acids at conserved locations, and are relatively small and often basic. The aromatic and cationic side chains may provide a powerful combination promoting and maintaining surface adhesion.