title: Structural basis of preferential binding of fucose-containing saccharide by the Caenorhabditis elegans galectin LEC-6.
abstract: Galectins are a group of lectins that can bind carbohydrate chains containing β-galactoside units. LEC-6, a member of galectins of Caenorhabditis elegans, binds fucose-containing saccharides. We solved the crystal structure of LEC-6 in complex with galactose-β1,4-fucose (Galβ1-4Fuc) at 1.5 Å resolution. The overall structure of the protein and the identities of the amino-acid residues binding to the disaccharide are similar to those of other galectins. However, further structural analysis and multiple sequence alignment between LEC-6 and other galectins indicate that a glutamic acid residue (Glu67) is important for the preferential binding between LEC-6 and the fucose moiety of the Galβ1-4Fuc unit. Frontal affinity chromatography analysis indicated that the affinities of E67D and E67A mutants for Galβ1-4Fuc are lower than that of wild-type LEC-6. Furthermore, the affinities of Glu67 mutants for an endogenous oligosaccharide, which contains a Galβ1-4Fuc unit, are drastically reduced relative to that of the wild-type protein. We conclude that the Glu67 in the oligosaccharide-binding site assists the recognition of the fucose moiety by LEC-6.
authors.affiliation: Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Makyio
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Mayumi
authors.initials: M
authors.lastname: Tamura
authors.forename: Kazusa
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Hideyo
authors.initials: H
authors.lastname: Takahashi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Natsugari
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Arata
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kasai
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamada
authors.forename: Soichi
authors.initials: S
authors.lastname: Wakatsuki
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Kato
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D005643:Fucose / Q000737:chemistry*; D005690:Galactose / Q000737:chemistry; D037161:Galectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding
chemical_list: D029742:Caenorhabditis elegans Proteins; D037161:Galectins; C534045:LEC-6 protein, C elegans; D009844:Oligosaccharides; D005643:Fucose; D018698:Glutamic Acid; D005690:Galactose
keywords: Caenorhabditis elegans; crystal structure; frontal affinity chromatography; galactose β1-4 fucose; galectin