1qmo

From Proteopedia

Revision as of 11:39, 20 March 2008

STRUCTURE OF FRIL, A LEGUME LECTIN THAT DELAYS HEMATOPOIETIC PROGENITOR MATURATION

Overview

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.

About this Structure

1QMO is a Protein complex structure of sequences from Lablab purpureus. Full crystallographic information is available from OCA.

Reference

The role of weak protein-protein interactions in multivalent lectin-carbohydrate binding: crystal structure of cross-linked FRIL., Hamelryck TW, Moore JG, Chrispeels MJ, Loris R, Wyns L, J Mol Biol. 2000 Jun 16;299(4):875-83. PMID:10843844

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