Schistosoma mansoni: surface membrane isolation with lectin-coated beads.

Lectins from Lens culinaris and Arachis hypogaea immobilized on polyacrylamide beads were used for selective isolation of glycosylated surface membrane domains of adult Schistosoma mansoni worms, and the method was compared with the membrane isolation procedure developed with polycationic (Affi-Gel) beads. The lentil lectin proved to be suitable for interaction with surface membrane components: an increment in the specific activities of tegumental phosphohydrolases was observed in the bound fraction with respect to that observed in a total worm homogenate. A characteristic polypeptide pattern on gel electrophoresis was also seen, more restricted than that obtained with the bound Affi-Gel fraction. Immobilized peanut lectin was not successful as a method for isolating membrane material from the tegument of adult worms. Solubilization and dissociation of the lentil lectin-bound enzyme markers was achieved after addition of detergent and competing sugars. Glycosylation of the solubilized enzymes was further confirmed by affinity chromatography with fresh lentil lectin-coated beads. These results, together with histochemical evidences, suggest that the active sites of some of these enzymes are located within or close to the cytoplasmic leaflet of the surface tegumental membranes, and allow us to propose a model for the double surface membrane complex where some proteins may be crossing the two bilayers.