Characterization of fucose-binding lectins in rock- and mud-dwelling snails inhabiting Kuwait Bay

Two novel lectins that bind selectively to trematode-associated fucosylated determinants have been characterized and purified from the hemolymph of wild-type rock-dwelling Turbo coronatus and mud-dwelling Cerithidea cingulata snails inhabiting Kuwait Bay. Both lectins were separately purified from the hemolymph of T. coronatus (designated Tc lectin) and C. cingulata (designated Cc lectin) by affinity chromatography on immobilized l-fucose-agarose columns and elution with a gradient of 0.1-1 M l-fucose. Assessments of the structural characteristics, by one- and two-dimensional polyacrylamide gel electrophoresis, indicated that Tc and Cc lectins were structurally distinct, and exist in their native forms as multimers of non-covalently associated subunits of different sizes and pIs. Removal of N-linked glycans by endo-β-N-acetylglucosaminidase F resolved the heterodisperse pattern of Tc lectin subunits into 31 and 27 kDa components (each with a pI of 7.8) as well as an 8 kDa component with a pI of 7.2, and collapsed the size microheterogeneity of the Cc lectin subunits into a single spot of 33 kDa (pI 5.4). Each of these subunits is subjected to differential post-translational N-linked glycosylations, which involve variable acidic complex-type units in Tc lectin and neutral high-mannose-type units in Cc lectin. Based on trematode glycoprotein binding and inhibition assays, the two lectins exhibited optimum binding at a similar pH range, but were distinct in terms of their temperature stability as well as binding affinities towards the fucose moiety constituting the fucosylated target.