title: Garlic (Allium sativum) lectins bind to high mannose oligosaccharide chains.
abstract: Two mannose-binding lectins, Allium sativum agglutinin (ASA) I (25 kDa) and ASAIII (48 kDa), from garlic bulbs have been purified by affinity chromatography followed by gel filtration. The subunit structures of these lectins are different, but they display similar sugar specificities. Both ASAI and ASAIII are made up of 12.5- and 11.5-kDa subunits. In addition, a complex (136 kDa) comprising a polypeptide chain of 54 +/- 4 kDa and the subunits of ASAI and ASAIII elutes earlier than these lectins on gel filtration. The 54-kDa subunit is proven to be alliinase, which is known to form a complex with garlic lectins. Constituent subunits of ASAI and ASAIII exhibit the same sequence at their amino termini. ASAI and ASAIII recognize monosaccharides in mannosyl configuration. The potencies of the ligands for ASAs increase in the following order: mannobiose (Manalpha1-3Man) < mannotriose (Manalpha1-6Manalpha1-3Man) approximately mannopentaose << Man9-oligosaccharide. The addition of two GlcNAc residues at the reducing end of mannotriose or mannopentaose enhances their potencies significantly, whereas substitution of both alpha1-3- and alpha1-6-mannosyl residues of mannotriose with GlcNAc at the nonreducing end increases their activity only marginally. The best manno-oligosaccharide ligand is Man9GlcNAc2Asn, which bears several alpha1-2-linked mannose residues. Interaction with glycoproteins suggests that these lectins recognize internal mannose as well as bind to the core pentasaccharide of N-linked glycans even when it is sialylated. The strongest inhibitors are the high mannose-containing glycoproteins, which carry larger glycan chains. Indeed, invertase, which contains 85% of its mannose residues in species larger than Man20GlcNAc, exhibited the highest binding affinity. No other mannose- or mannose/glucose-binding lectin has been shown to display such a specificity.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
authors.forename: T K
authors.initials: TK
authors.lastname: Dam
authors.forename: K
authors.initials: K
authors.lastname: Bachhawat
authors.forename: P G
authors.initials: PG
authors.lastname: Rani
authors.forename: A
authors.initials: A
authors.lastname: Surolia
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive / Q000502:physiology; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D013437:Carbon-Sulfur Lyases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D005737:Garlic / Q000737:chemistry* / Q000201:enzymology; D006023:Glycoproteins / Q000378:metabolism / Q000494:pharmacology; D006026:Glycoside Hydrolases / Q000378:metabolism; D006384:Hemagglutination / Q000187:drug effects; D037102:Lectins / Q000378:metabolism*; D037241:Mannose-Binding Lectins; D008362:Mannosides / Q000737:chemistry*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism* / Q000494:pharmacology; D037121:Plant Lectins; D010946:Plants, Medicinal; D011485:Protein Binding; D017421:Sequence Analysis; D043324:beta-Fructofuranosidase
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D037102:Lectins; D037241:Mannose-Binding Lectins; D008362:Mannosides; D009844:Oligosaccharides; D037121:Plant Lectins; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D013437:Carbon-Sulfur Lyases; C019243:alliin lyase