Evidence for a family of schistosome glycan-binding lectins in Biomphalaria alexandrina.
A novel family of isolectins that selectively recognize a schistosome-associated fucosyllactose determinant was identified in the hemolymph of Biomphalaria alexandrina, a snail vector of Schistosoma mansoni. Three lectins of this family were purified by serial affinity chromatography on a column of L-fucose and elution with a gradient of 0.1-1 M L-fucose (designated BaSII and BaSIII), followed by a column of D-glucose and elution with 0.3 M D-glucose (designated BaSI). Assessment of the structural characteristics by one- and two-dimensional gels indicated that, inspite of similarities in native molecular weights, the three lectins were tetramers of noncovalently-associated subunits that were of different sizes and pIs in BaSI, and of equal size but distinct pIs in BaSII and BaSIII. Comparisons of two-dimensional gels of the glycosylated and deglycosylated forms were consistent with the presence of an invariant alpha subunit (13.2 kDa, pI 7.2) constituting the three deglycosylated lectins, which associates with other subunits unique to each lectin, namely a beta subunit (10.1 kDa, pI 5.8) in BaSI, an alpha 1 subunit (13.2 kDa, pI 6.8) in BaSII and BaSIII, and an alpha 2 subunit (13.2 kDa, pI 7.0) in BaSIII. Each of these subunits is subjected to differential post-translational N-linked glycosylations, which accounts for the additional heterogeneity expressed by the glycosylated lectins. Based on miracidial glycoprotein binding and inhibition assays, the three lectins exhibited optimum binding at similar pH and temperature, but were distinct in their binding affinities towards the fucose moiety constituting the fucosyllactose target. These observations indicate that an oligomorphic family of recognition molecules may have evolved to regulate the snails' response to schistosomes.
Mansour
M H
MH
Department of Zoology, Cairo University, Egypt.
D000818:Animals; D001700:Biomphalaria / Q000737:chemistry*; D002846:Chromatography, Affinity; D015180:Electrophoresis, Gel, Two-Dimensional; D006385:Hemagglutination Inhibition Tests; D006458:Hemolymph / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D037102:Lectins / Q000737:chemistry / Q000302:isolation & purification*; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D012550:Schistosoma mansoni / Q000737:chemistry*; D013696:Temperature
D037102:Lectins; D011134:Polysaccharides