The role of weak protein-protein interactions in multivalent lectin-carbohydrate binding: crystal structure of cross-linked FRIL.

TitleThe role of weak protein-protein interactions in multivalent lectin-carbohydrate binding: crystal structure of cross-linked FRIL.
Publication TypeJournal Article
Year of Publication2000
AuthorsHamelryck, T. W., J. G. Moore, M. J. Chrispeels, R. Loris, and L. Wyns
JournalJ Mol Biol
Volume299
Issue4
Pagination875-83
Date Published2000 Jun 16
ISSN0022-2836
KeywordsBinding Sites, Carbohydrate Conformation, Carbohydrate Sequence, Concanavalin A, Cross-Linking Reagents, Crystallography, X-Ray, Dimerization, Fabaceae, Hydrogen Bonding, Lectins, Mannose, Mannose-Binding Lectins, Models, Molecular, Molecular Sequence Data, Plant Lectins, Plants, Medicinal, Protein Binding, Protein Structure, Quaternary, Protein Structure, Secondary, Substrate Specificity, Trisaccharides
Abstract

Binding of multivalent glycoconjugates by lectins often leads to the formation of cross-linked complexes. Type I cross-links, which are one-dimensional, are formed by a divalent lectin and a divalent glycoconjugate. Type II cross-links, which are two or three-dimensional, occur when a lectin or glycoconjugate has a valence greater than two. Type II complexes are a source of additional specificity, since homogeneous type II complexes are formed in the presence of mixtures of lectins and glycoconjugates. This additional specificity is thought to become important when a lectin interacts with clusters of glycoconjugates, e.g. as is present on the cell surface. The cryst1al structure of the Glc/Man binding legume lectin FRIL in complex with a trisaccharide provides a molecular snapshot of how weak protein-protein interactions, which are not observed in solution, can become important when a cross-linked complex is formed. In solution, FRIL is a divalent dimer, but in the crystal FRIL forms a tetramer, which allows for the formation of an intricate type II cross-linked complex with the divalent trisaccharide. The dependence on weak protein-protein interactions can ensure that a specific type II cross-linked complex and its associated specificity can occur only under stringent conditions, which explains why lectins are often found forming higher-order oligomers.

DOI10.1006/jmbi.2000.3785
Alternate JournalJ. Mol. Biol.
PubMed ID10843844