Abstract
Only a few animal phyla have been screened for the presence and distribution of lectins. Probably the most intensively studied group is the mollusk. In this investigation, 22 species from 12 families of tropical sponges collected in Los Roques National Park (Venezuela) were screened for the presence of lectins. Nine saline extracts exhibited strong hemagglutinating activity against pronase-treated hamster red blood cells; five of these reacted against rabbit red blood cells, four with trypsin-treated bovine red blood cells, and five with human red blood cells regardless of the blood group type. Extracts from the three species studied from genus Aplysina (archeri, lawnosa, and cauliformis) were highly reactive and panagglutinating against the panel of red blood cells tested. The lectins from A. archeri and A. lawnosa 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 mass of 63 kDa and by SDS-polyacrylamide gel electrophoresis under reducing conditions have an apparent molecular mass of 16 kDa, thus suggesting they occur as homotetramers. The purified lectins contain 3-4 mol of divalent cation 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 preference of the lectin for nonreducing beta-linked d-Gal residues being the best inhibitors of red blood cells binding methyl-beta-d-Gal and thiodigalactoside (Gal beta 1-4-thiogalactopyranoside). The behavior of several glycans on immobilized lectin affinity chromatography confirmed and extended the specificity data obtained by hapten inhibition.
Highlights
A few animal phyla have been screened for the presence and distribution of lectins
In an effort to identify lectins with novel affinity properties, we studied 22 species from 12 families of tropical sponges for the presence of hemagglutinating activity against a panel of normal or protease-treated red blood cells from different species
The results presented in this report show that the presence of lectins in marine sponges is not as widespread as in other marine organisms or in plants
Summary
The most intensively studied group is the mollusk In this investigation, 22 species from 12 families of tropical sponges collected in Los Roques National Park (Venezuela) were screened for the presence of lectins. The lectins from A. archeri and A. lawnosa were purified to homogeneity by ammonium sulfate fractionation, affinity chromatography on p-aminobenzyl--1-thiogalactopyranoside-agarose, and gel filtration chromatography. Both lectins exhibited a native molecular mass of 63 kDa and by SDS-polyacrylamide gel electrophoresis under reducing conditions have an apparent molecular mass of 16 kDa, suggesting they occur as homotetramers. Hapten inhibition of hemagglutination was carried out to define the sugar binding specificity of the purified A. archeri lectin. We present information on the nature and specificity of their combining site as examined by hapten inhibition experiments and affinity chromatography
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