Isolation and characterization of a second lectin (SNA-II) present in elderberry (Sambucus nigra L.) bark.
A second lectin (SNA-II) has been isolated from elderberry (Sambucus nigra L.) bark by affinity chromatography on immobilized asialo-glycophorin. This lectin is a blood group nonspecific glycoprotein containing 7.8% carbohydrate and which is rich in asparagine/aspartic acid, glutamine/glutamic acid, glycine, valine, and leucine. Gel filtration on Superose 12 gave a single symmetrical peak corresponding to Mr, 51,000; SDS-acrylamide electrophoresis gave a single polypeptide, Mr, 30,000. Hence SNA-II appears to be a homodimer. The lectin is a Gal/GalNAc-specific lectin which is precipitated by glycoproteins containing GalNAc-terminated oligosaccharide chains (e.g., asialo-ovine submaxillary and hog gastric mucins), and by glycoproteins and polysaccharides having multiple terminal nonreducing D-galactosyl groups as occur in asialoglycophorin, asialo-laminin and Type 14 pneumococcal polysaccharide. The carbohydrate binding specificity of SNA-II was studied by sugar hapten inhibition of the asialo-glycophorin precipitation reaction. The lectin's binding site appears to be most complementary to Gal-NAc linked alpha to the C-2, C-3, or C-6 hydroxyl group of galactose. These disaccharide units are approximately 100 times more potent than melibiose, 60 times more potent than N-acetyllactosamine, and 30 times more potent than lactose. Interestingly, the blood group A-active trisaccharide containing an L-fucosyl group linked alpha 1-2 to galactose was 10-fold poorer as an inhibitor than the parent oligosaccharide (GalNAc alpha 1-3Gal), suggesting steric hindrance to binding by the alpha-L-fucosyl group; this explains the failure of the lectin to exhibit blood group A specificity.
Kaku
H
H
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109.
Peumans
W J
WJ
Goldstein
I J
IJ
D000595:Amino Acid Sequence; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002241:Carbohydrates; D002846:Chromatography, Affinity / Q000379:methods; D004187:Disaccharides; D004591:Electrophoresis, Polyacrylamide Gel; D037102:Lectins / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009844:Oligosaccharides / Q000302:isolation & purification; D037121:Plant Lectins; D011233:Precipitin Tests; D054788:Ribosome Inactivating Proteins; D012276:Ricin; D012689:Sequence Homology, Nucleic Acid
D002241:Carbohydrates; D004187:Disaccharides; D037102:Lectins; D009844:Oligosaccharides; D037121:Plant Lectins; C050600:Sambucus nigra lectins; D012276:Ricin; D054788:Ribosome Inactivating Proteins