title: X-ray crystal structure of a pea lectin-trimannoside complex at 2.6 A resolution.
abstract: The x-ray crystal structure of pea lectin, in complex with a methyl glycoside of the N-linked-type oligosaccharide trimannosyl core, methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, has been solved by molecular replacement and refined at 2.6-A resolution. The R factor is 0.183 for all data in the 8.0 to 2.6 A resolution range with an average atomic temperature factor of 26.1 A2. Strong electron density for a single mannose residue is found in the monosaccharide-binding site suggesting that the trisaccharide binds primarily through one of the terminal alpha-linked mannose residues. The complex is stabilized by hydrogen bonds involving the protein residues Asp-81, Gly-99, Asn-125, Ala-217, and Glu-218, and the carbohydrate oxygen atoms O3, O4, O5, and O6. In addition, the carbohydrate makes van der Waals contacts with the protein, involving Phe-123 in particular. These interactions are very similar to those found in the monosaccharide complexes with concanavalin A and isolectin 1 of Lathyrus ochrus, confirming the structural relatedness of this family of proteins. Comparison of the pea lectin complex with the unliganded pea lectin and concanavalin A structures indicates differences in the conformation and water structure of the unliganded binding sites of these two proteins. Furthermore, a correlation between the position of the carbohydrate oxygen atoms in the complex and the bound water molecules in the unliganded binding sites is found. Binding of the trimannose core through a single terminal monosaccharide residue strongly argues that an additional fucose-binding site is responsible for the high affinity pea lectin-oligosaccharide interactions.
authors: Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.
authors: J M
authors: JM
authors: Rini
authors: K D
authors: KD
authors: Hardman
authors: H
authors: H
authors: Einspahr
authors: F L
authors: FL
authors: Suddath
authors: J P
authors: JP
authors: Carver
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006020:Glycopeptides / Q000737:chemistry; D006860:Hydrogen Bonding; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D008358:Mannose; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D037121:Plant Lectins; D011485:Protein Binding; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D006020:Glycopeptides; D037102:Lectins; D009844:Oligosaccharides; D037121:Plant Lectins; C036292:pea lectin; D008358:Mannose