The primary structure of the acidic lectin from winged bean (Psophocarpus tetragonolobus): insights in carbohydrate recognition, adenine binding and quaternary association

The amino acid sequence of the winged bean acidic lectin (WBA II) mas deter mined by chemical means and by recombinant techniques. From the N- and C-te rminal sequence, obtained chemically, primers were designed for PCR amplifi cation of the genomic DNA. The PCR product was cloned and sequenced to get the complete primary structure of WBA. II. Peptide fragments for sequencing were also obtained by tryptic cleavages of the native lectin, The WBA II s equence showed a high degree of homology with that of WBA I and Erythrina c orallodendron lectin (ECorL), especially in the regions involved in subunit association, where there is a very high conservation of residues. This per haps implies the importance of this particular region in subunit interactio ns in this lectin, In addition, many of the residues, involved in carbohydr ate binding in legume lectins, appear to be conserved in WBA II, The distin ct differences in anomeric specificity observed amongst WBA I, WBA II, ECor L and peanut agglutinin (PNA) may be explained by subtle differences in seq uence/structure of their D-loops, WBA II binds adenine quite strongly; a pu tative adenine binding sequence has been identified. (C) 2000 Federation of European Biochemical Societies.