Structural basis for chitotetraose coordination by CGL3, a novel galectin-related protein from Coprinopsis cinerea |
| |
Authors: | Wälti Martin Andreas Walser Piers Jamie Thore Stéphane Grünler Anke Bednar Michaela Künzler Markus Aebi Markus |
| |
Affiliation: | 1 Institute of Microbiology, ETH Zürich, Wolfgang-Pauli-Str. 10, CH-8093 Zürich, Switzerland 2 Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia 3 Institute of Molecular Biology and Biophysics, ETH Zürich, Schafmattstr. 20, CH-8093 Zürich, Switzerland |
| |
Abstract: | Recent advances in genome sequencing efforts have revealed an abundance of novel putative lectins. Among these, many galectin-related proteins, characterized by many conserved residues but intriguingly lacking critical amino acids, have been found in all corners of the eukaryotic superkingdom. Here we present a structural and biochemical analysis of one representative, the galectin-related lectin CGL3 found in the inky cap mushroom Coprinopsis cinerea. This protein contains all but one conserved residues known to be involved in β-galactoside binding in galectins. A Trp residue strictly conserved among galectins is changed to an Arg in CGL3 (R81). Accordingly, the galectin-related protein is not able to bind lactose. Screening of a glycan array revealed that CGL3 displays preference for oligomers of β1-4-linked N-acetyl-glucosamines (chitooligosaccharides) and GalNAcβ1-4GlcNAc (LacdiNAc). Carbohydrate-binding affinity of this novel lectin was quantified using isothermal titration calorimetry, and its mode of chitooligosaccharide coordination not involving any aromatic amino acid residues was studied by X-ray crystallography. Structural information was used to alter the carbohydrate-binding specificity and substrate affinity of CGL3. The importance of residue R81 in determining the carbohydrate-binding specificity was demonstrated by replacing this Arg with a Trp residue (R81W). This single-amino-acid change led to a lectin that failed to bind chitooligosaccharides but gained lactose binding. Our results demonstrate that, similar to the legume lectin fold, the galectin fold represents a conserved structural framework upon which dramatically altered specificities can be grafted by few alterations in the binding site and that, in consequence, many metazoan galectin-related proteins may represent lectins with novel carbohydrate-binding specificities. |
| |
Keywords: | LacdiNAc, GalNAcβ1-4GlcNAc CRD, carbohydrate-recognition domain CLC, Charcot-Leyden crystal protein His8-CGL3, N-terminally His-tagged CGL3 LacNAc, Galβ1-4GlcNAc ITC, isothermal titration calorimetry WT, wild type TBS, Tris-buffered saline NCS, noncrystallographic symmetry PDB, Protein Data Bank CFG, Consortium for Functional Glycomics |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|