AMINO-ACID-SEQUENCE AND 3-DIMENSIONAL STRUCTURE OF THE TN-SPECIFIC ISOLECTIN B4 FROM VICIA-VILLOSA

The partial amino acid sequence of the tetrameric isolectin B4 from Vi cia villosa seeds has been determined by peptide analysis, and its thr ee-dimensional structure solved by molecular replacement techniques an d refined at 2.9 Angstrom resolution to a crystallographic R-factor of 21%. Each subunit displays the thirteen-stranded beta-barrel topology characteristic of legume lectins, The amino acid residues involved in metal- and sugar-binding are similar to those of other GalNAc-specifi c lectins, indicating that residues outside the carbohydrate-binding p ocket modulate the affinity for the Tn glycopeptide, Isolectin B4 disp lays an unusual quaternary structure, probably due to protein glycosyl ation. (C) 1997 Federation of European Biochemical Societies.