A Comparative Study of Mannose-binding Lectins from the Amaryllidaceae and Alliaceae

A comparative study of the lectins from the families Amaryllidaceae and Alliaceae reveals many common features: all bind D-mannose exclusively and have similar molecular structures and amino acid compositions. All these lectins contain subunits of M, 11500-14000 which are not linked by disulphide bonds and occur as dimers (in Allium sativum, A. vineale, A. ursinum, A. moly, Narcissus pseudonarcissus and Clivia miniata) or tetramers (in Galanthus nivalis, Hippeastrum hybrid, Allium cepa and A. porrum. Most of these lectins were shown to occur as complex mixtures of isolectins. In general, the lectin concentration in Amaryllidaceae bulbs is higher than in Alliaceae bulbs. Antisera raised in rabbits against the Galanthus nivalis and the Narcissus cv Carlton lectins gave, upon double immunodiffusion, single precipitation bands and lines of identity with purified lectins from all Amaryllidaceae species, A. cepa and A. porrum. Similar single lines of identity were obtained between purified lectins from other Allium species and Amaryllidaceae lectins when challenged with rabbit anti-daffodil antiserum. However, two immunoprecipitin bands were obtained when the same assay was carried out with antiserum against Galanthus nivalis lectin, one line cross-reacting with the Amaryllidaceae lectins with the formation of a spur. Cross-reactions were also observed between Allium cepa and A. porrum lectins and the lectins from A. moly, A. vineale, A. ursinum and A. sativum. Although all lectins are serologically related, there are differences in their reaction with various antisera.