Selective binding of N-acetylglucosamine to the chicken hepatic lectin.
Among Ca2+-dependent (C-type) animal lectins, the chicken hepatic lectin (CHL) is unique in displaying almost complete selectivity for N-acetylglucosamine over other monosaccharide ligands. The crystal structures of the carbohydrate-recognition domain (CRD) from serum mannose-binding protein (MBP) and of a complex between the CRD from liver MBP and the methyl glycoside of N-acetylglucosamine were used to model the binding site in CHL. Substitution of portions of CHL into the MBP framework did not substantially increase selectivity. A bacterial expression system for the CRD of CHL was developed so that specific residues predicted to be near the 2-acetamido substituent of N-acetylglucosamine could be altered by site-directed mutagenesis. The results indicate that the ligand is bound to CHL in the same orientation as it binds to liver MBP. A tyrosine and a valine residue that probably contact the the N-acetyl group have been identified. These results, together with studies of ligand-binding selectivity, suggest that these residues form part of a binding pocket for the N-acetyl group, which confers selective binding of N-acetylglucosamine.
Burrows
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Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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Drickamer
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D000117:Acetylglucosamine / Q000737:chemistry / Q000378:metabolism*; D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D037263:Asialoglycoprotein Receptor; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry; D002645:Chickens; D004705:Endocytosis; D037241:Mannose-Binding Lectins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013379:Substrate Specificity
D037263:Asialoglycoprotein Receptor; D002352:Carrier Proteins; D037241:Mannose-Binding Lectins; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D000409:Alanine; D000117:Acetylglucosamine