title: Identification of novel contributions to high-affinity glycoprotein-receptor interactions using engineered ligands.
abstract: Engineered receptor fragments and glycoprotein ligands employed in different assay formats have been used to dissect the basis for the dramatic enhancement of binding of two model membrane receptors, dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) and the macrophage galactose lectin, to glycoprotein ligands compared to simple sugars. These approaches make it possible to quantify the importance of two major factors that combine to enhance the affinity of single carbohydrate-recognition domains (CRDs) for glycoprotein ligands by 100-to 300-fold. First, the presence of extended binding sites within a single CRD can enhance interaction with branched glycans, resulting in increases of fivefold to 20-fold in affinity. Second, presentation of glycans on a glycoprotein surface increases affinity by 15-to 20-fold, possibly due to low-specificity interactions with the surface of the protein or restriction in the conformation of the glycans. In contrast, when solution-phase networking is avoided, enhancement due to binding of multiple branches of a glycan to multiple CRDs in the oligomeric forms of these receptors is minimal and binding of a receptor oligomer to multiple glycans on a single glycoprotein makes only a twofold contribution to overall affinity. Thus, in these cases, multivalent interactions of individual glycoproteins with individual receptor oligomers have a limited role in achieving high affinity. These findings, combined with considerations of membrane receptor geometry, are consistent with the idea that further enhancement of the binding to multivalent glycoprotein ligands requires interaction of multiple receptor oligomers with the ligands.
authors.affiliation: Division of Molecular Biosciences, Department of Life Sciences, Imperial College, London SW7 2AZ, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Coombs
authors.forename: Rebecca
authors.initials: R
authors.lastname: Harrison
authors.forename: Samantha
authors.initials: S
authors.lastname: Pemberton
authors.forename: Adrián
authors.initials: A
authors.lastname: Quintero-Martinez
authors.forename: Simon
authors.initials: S
authors.lastname: Parry
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Haslam
authors.forename: Anne
authors.initials: A
authors.lastname: Dell
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Taylor
authors.forename: Kurt
authors.initials: K
authors.lastname: Drickamer
mesh_terms: D015815:Cell Adhesion Molecules / Q000378:metabolism*; D005936:Glucans / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D037181:Lectins, C-Type / Q000378:metabolism*; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D015815:Cell Adhesion Molecules; D005936:Glucans; D006023:Glycoproteins; D037181:Lectins, C-Type; D011956:Receptors, Cell Surface; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C506225:MGL lectin, human