Lectins from tropical sponges - Purification and characterization of lectins from genus Aplysina

Only a few animal phyla have been screened for the presence and distributio n of lectins, Probably the most intensively studied group is the mollusk. I n this investigation, 22 species from 12 families of tropical sponges colle cted in Los Rogues National Park (Venezuela) were screened for the presence of lectins. Nine saline extracts exhibited strong hemagglutinating activit y against pronase-treated hamster red blood cells; five of these reacted ag ainst rabbit red blood cells, four with trypsin-treated bovine red blood ce lls, and five with human red blood cells regardless of the blood group type . Extracts from the three species studied from genus Aplysina (archeri, law nosa, and cauliformis) were highly reactive and panagglutinating against th e panel of red blood cells tested. The lectins from A. archeri and A. lawno sa were purified to homogeneity by ammonium sulfate fractionation, affinity chromatography on p-aminobenzyl-beta-1-thiogalactopyranoside-agarose, and gel filtration chromatography. Both lectins exhibited a native molecular ma ss of 63 kDa and by SDS-polyacrylamide gel electrophoresis under reducing c onditions have an apparent molecular mass of 16 kDa, thus suggesting they o ccur as homotetramers. The purified lectins contain 3-4 mol of divalent cat ion per molecule, which are essential for their biological activity. Hapten inhibition of hemagglutination was carried out to define the sugar binding specificity of the purified A. archeri lectin. The results indicate a pref erence of the lectin for nonreducing beta-linked D-Gal residues being the b est inhibitors of red blood cells binding methyl-beta-D-Gal and thiodigalac toside (Gal beta 1-4-thiogalactopyranoside). The behavior of several glycan s on immobilized lectin affinity chromatography confirmed and extended the specificity data obtained by hapten inhibition.