Characterization of Biomphalaria alexandrina-derived lectins recognizing a fucosyllactose-related determinant on...

Two novel lectins that bind selectively to a schistosome-associated fucosyllactose-related determinant have been characterized and purified from the hemolymph of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni. Both lectins were purified by affinity chromatography on a column of equimolar mixture of D- and L-glucose coupled to epoxy-activated Sepharose 6B and sequential elution by D-glucose (designated BaSI) and L-fucose (designated BaSII). Assessment of the structural characteristics, by one- and two-dimensional polyacrylamide gel electrophoresis, indicated that BaSI and BaSII were structurally distinct, and exist in their native forms as multimers of non-covalently associated subunits, that were of different sizes in BaSI and of equal size in BaSII. Removal of N-linked glycans by Endo-beta-N-acetylglucosaminidase F resolved the heterodisperse pattern of BaSI subunits into two spots of 13.2 kDa (pI 7.2) and 10.1 kDa (pI 5.8), and collapsed the acidic charge microheterogeneity of the BaSII subunit into a single spot that corresponded in terms of molecular weight and pI to the basic 13.2-kDa subunit of BaSI. In miracidial binding and inhibition assays with different sugars, both lectins exhibited selectivity towards a fucosyllactose sequence, but BaSII had a higher binding preference to fucose moieties. BaSII-Sepharose 4B affinity chromatography and analysis on two-dimensional gels indicated that multiple copies of the fucosyllactose-related determinant were expressed by heterogeneous, acidic glycoproteins in the miracidial stage of S. mansoni.