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Structural basis for sugar recognition, including the Tn carcinoma antigen, by the lectin SNA‐II from Sambucus nigra
Author(s) -
Maveyraud Laurent,
Niwa Hideaki,
Guillet Valérie,
Svergun Dmitri I.,
Konarev Peter V.,
Palmer Rex A.,
Peumans Willy J.,
Rougé Pierre,
Van Damme Els J. M.,
Reynolds Colin D.,
Mourey Lionel
Publication year - 2009
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.22222
Subject(s) - sambucus nigra , lectin , chemistry , agglutinin , ricin , crystal structure , stereochemistry , crystallography , biochemistry , toxin
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 Å and 1.35 Å, respectively. In both crystal forms, the SNA‐II molecule folds into two linked ββ‐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, αα1‐methylgalactose, fucose, and the carcinoma‐specific Tn antigen) were determined at 1.55 Å 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. Proteins 2009. © 2008 Wiley‐Liss, Inc.