title: Structural basis for the carbohydrate-specificity of basic winged-bean lectin and its differential affinity for Gal and GalNAc.
abstract: The crystal structure of the complexes of basic winged-bean lectin with galactose, 2-methoxygalactose, N-acetylgalactosamine and methyl-alpha-N-acetylgalactosamine have been determined. Lectin-sugar interactions involve four hydrogen bonds and a stacking interaction in all of the complexes. In addition, an N-H...O hydrogen bond involving the hydroxyl group at C2 exists in the galactose and 2-methoxygalactose complexes. An additional hydrophobic interaction involving the methyl group in the latter leads to the higher affinity of the methyl derivative. In the lectin-N-acetylgalactosamine complex the N-H...O hydrogen bond is lost, but a compensatory hydrogen bond is formed involving the O atom of the acetamido group. In addition, the CH(3) moiety of the acetamido group is involved in hydrophobic interactions. Consequently, the 2-methyl and acetamido derivatives of galactose have nearly the same affinity for the lectin. The methyl group alpha-linked to the galactose takes part in additional hydrophobic interactions. Therefore, methyl-alpha-N-acetylgalactosamine has a higher affinity than N-acetylgalactosamine for the lectin. The structures of basic winged-bean lectin-sugar complexes provide a framework for examining the relative affinity of galactose and galactosamine for the lectins that bind to them. The complexes also lead to a structural explanation for the blood-group specificity of basic winged-bean lectin.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
authors.forename: Kiran A
authors.initials: KA
authors.lastname: Kulkarni
authors.forename: Samiksha
authors.initials: S
authors.lastname: Katiyar
authors.forename: Avadhesha
authors.initials: A
authors.lastname: Surolia
authors.forename: Mamannamana
authors.initials: M
authors.lastname: Vijayan
authors.forename: Kaza
authors.initials: K
authors.lastname: Suguna
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry* / Q000378:metabolism; D001789:Blood Group Antigens / Q000737:chemistry / Q000378:metabolism; D005690:Galactose / Q000737:chemistry* / Q000378:metabolism; D037161:Galectins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D037121:Plant Lectins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
chemical_list: D001789:Blood Group Antigens; D037161:Galectins; D037121:Plant Lectins; C049304:winged bean lectin; D000116:Acetylgalactosamine; D005690:Galactose