title: Phytohemagglutinin from Phaseolus vulgaris (PHA-E) displays a novel glycan recognition mode using a common legume lectin fold.
abstract: Phytohemagglutinin from Phaseolus vulgaris (PHA-E), a legume lectin, has an unusual specificity toward biantennary galactosylated N-glycan with bisecting N-acetylglucosamine (GlcNAc). To investigate the interaction in detail, we have solved the crystal structures of PHA-E without ligand and in complex with biantennary N-glycan derivatives. PHA-E interacts with the trisaccharide unit (Galβ1-4GlcNAcβ1-2Man) in a manner completely different from that of mannose/glucose-specific legume lectins. The inner mannose residue binds to a novel site on the protein, and its rotation is opposite to that occurring in the monosaccharide-binding site of other lectins around the sugar O3 axis. Saturation-transfer difference NMR using biantennary di-galactosylated and bisected glycans reveals that PHA-E interacts with both antennas almost equally. The unique carbohydrate interaction explains the glycan-binding specificity and high affinity.
authors.affiliation: Structural Glycobiology Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, RIKEN Global Research Cluster, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Nagae
authors.forename: Keisuke
authors.initials: K
authors.lastname: Soga
authors.forename: Kana
authors.initials: K
authors.lastname: Morita-Matsumoto
authors.forename: Shinya
authors.initials: S
authors.lastname: Hanashima
authors.forename: Akemi
authors.initials: A
authors.lastname: Ikeda
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamaguchi
mesh_terms: D008958:Models, Molecular; D008968:Molecular Conformation; D027805:Phaseolus / Q000737:chemistry*; D010835:Phytohemagglutinins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010835:Phytohemagglutinins; D011134:Polysaccharides; C067494:erythroagglutinating phytohemagglutinin
keywords: N-glycan; NMR; X-ray crystallography; legume lectin; protein–carbohydrate interaction