Isolation and characterization of three Ca2+-dependent β-galactoside-specific lectins from snake venoms

Three lactose-inhibited lectins from the venoms of the snakes Agkistrodon contortrix contortrix (southern copperhead), Ancistrodon piscivorous leukostoma (western cottonmouth moccasin) and Crotalus atrox (western diamondback rattlesnake) have been isolated and newly characterized. The three lectins are similar to thrombolectin, a lectin isolated from the venom of Bothrops atrox (fer-de-lance) (Gartner, Stocker & Williams, 1980), with regard to sugar specificity, Mr, Ca2+ requirements and sensitivity to reducing agents. Each lectin is a dimer (Mr 28 000) consisting of monomers (Mr 14 000) indistinguishable on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Haemagglutination activity is dependent on the presence of Ca2+ and is inhibited by reducing agents. The lectins are not identical and can be distinguished on the basis of relative affinities for inhibiting sugars, isoelectric points and immunoprecipitation assays using anti-(cottonmouth lectin) serum.