LECTINS FROM THE HORSESHOE CRAB, LIMULUS POLYPHEMUS, REACTIVE WITH BACTERIAL LIPOPOLYSACCHARIDE
The Limulus serum is capable of precipitating various components of the lipopolysaccharide molecule from R mutants of Salmonella minnesota. Precipitation-inhibition studies using 2-keto-3-deoxyoctonate (KDO) have supported the hypothesis that this acidic residue is the immunodeterminant group in the core region of the lipopolysaccharide molecule. Limulus also contains a lectin which interacts with the lipid A region of lipopolysaccharide; the proposed binding site in this region is the glucosamine backbone of the lipid A molecule. A sialic acid-binding lectin from the serum of the horseshoe crab, Limulus polyphemus, was isolated by preparative polyacrylamide slab gel electrophoresis and by ion-exchange chromatography on a column of diethylaminoethyl (DEAE)-Sephadex. The purified lectin precipitates the lipopolysaccharide molecules containing the KDO residue, and agglutinates chicken erythrocytes. This lectin does not bind to the glucosamine backbone of the lipid A. Hemagglutination and hemagglutination-inhibition studies, using untreated chicken erythrocytes and chicken erythrocytes coated with glycolipid from the Re mutant of S. minnesota indicated that the isolated lectin reacts with both N-acetylneuraminic acid and KDO. Cross-inhibition studies suggest that the same combining site on the lectin is involved in these reactions.
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