Structural basis for sugar recognition, including the Tn carcinoma antigen, by the lectin SNA-II from Sambucus nigra.
Bark of elderberry (Sambucus nigra) contains a galactose (Gal)/N-acetylgalactosamine (GalNAc)-specific lectin (SNA-II) corresponding to slightly truncated B-chains of a genuine Type-II ribosome-inactivating protein (Type-II RIPs, SNA-V), found in the same species. The three-dimensional X-ray structure of SNA-II has been determined in two distinct crystal forms, hexagonal and tetragonal, at 1.90 A and 1.35 A, respectively. In both crystal forms, the SNA-II molecule folds into two linked beta-trefoil domains, with an overall conformation similar to that of the B-chains of ricin and other Type-II RIPs. Glycosylation is observed at four sites along the polypeptide chain, accounting for 14 saccharide units. The high-resolution structures of SNA-II in complex with Gal and five Gal-related saccharides (GalNAc, lactose, alpha1-methylgalactose, fucose, and the carcinoma-specific Tn antigen) were determined at 1.55 A resolution or better. Binding is observed in two saccharide-binding sites for most of the sugars: a conserved aspartate residue interacts simultaneously with the O3 and O4 atoms of saccharides. In one of the binding sites, additional interactions with the protein involve the O6 atom. Analytical gel filtration, small angle X-ray scattering studies and crystal packing analysis indicate that, although some oligomeric species are present, the monomeric species predominate in solution.
Maveyraud
Laurent
L
Institut de Pharmacologie et de Biologie Structurale (IPBS), UMR 5089, Université Paul Sabatier Toulouse III/CNRS, Toulouse, France. laurent.maveyraud@ipbs.fr
Niwa
Hideaki
H
Guillet
Valérie
V
Svergun
Dmitri I
DI
Konarev
Peter V
PV
Palmer
Rex A
RA
Peumans
Willy J
WJ
Rougé
Pierre
P
Van Damme
Els J M
EJ
Reynolds
Colin D
CD
Mourey
Lionel
L
D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005690:Galactose / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D037121:Plant Lectins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D054788:Ribosome Inactivating Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D027924:Sambucus nigra / Q000737:chemistry* / Q000378:metabolism; D053838:Scattering, Small Angle; D014934:Wood / Q000737:chemistry
D015295:Antigens, Tumor-Associated, Carbohydrate; D037121:Plant Lectins; D011134:Polysaccharides; C050600:Sambucus nigra lectins; C040286:Tn antigen; D054788:Ribosome Inactivating Proteins; D005690:Galactose