Sponge aggregation factor and sponge hemagglutinin: Possible relationships between two different molecules

Abstract

A lectin from the marine sponge GEODIA CYDONIUM was isolated and characterized. GEODIA lectin (GL) agglutinates human red blood cells irrespective of the ABO blood group and precipitates with a variety of D-galactose containing glycosubstances, i.e. certain snail galactans, bovine erythrocyte glycoprotein and PNEUMOCOCCUS type XIV polysaccharide. The only simple sugars inhibiting the GL-mediated hemagglutination were lactose and n-acetyl-D-galactosamine.GL was purified by affinity chromatography on Sepharose 4B almost to homogeneity as tested by polyacrylamide disc gel electrophoresis. Positive staining of the lectin band with Coomassie brilliant blue and PAS suggest that GL is a glycoprotein. Under dissociating conditions GL exhibits an apparent mol. wt. of 12,000 daltons. The elution behaviour of the lectin on Biogel suggests that GL exists as an oligomeric molecule in its native state.Our data obtained with GL demonstrate that the species-specific aggregation factor (AF) from GEODIA is not identical with this lectin. Two major hypotheses for a biological role of GL are discussed: first, the cooperation of GL with AF in sorting-out processes of GEODIA cells and second, the possibility that GL is involved in defense mechanisms.