Ligand induced galectin-3 self-association.
Research output: Contribution to journal › Article
Many functions of galectin-3 entail binding of its carbohydrate recognition site to glycans of a glycoprotein, resulting in cross-linking thought to be mediated by its N-terminal non-carbohydrate-binding domain. Here we studied interaction of galectin-3 with the model glycoprotein asialofetuin (ASF), using a fluorescence anisotropy (FA) assay to measure the concentration of free galectin carbohydrate recognition sites in solution. Surprisingly, in the presence of ASF this remained low even at high galectin-3 concentrations, showing that many more galectin-3 molecules were engaged than expected due to the about 9 known glycan based binding sites per ASF molecule. This suggests that, after ASF induced nucleation, galectin-3 associates with itself by the carbohydrate recognition site binding to another galectin-3 molecule, possibly forming oligomers. We named this type-C self-association to distinguish it from the previously proposed models (type-N) where galectin-3 molecules bind to each other through the N-terminal domain, and all carbohydrate recognition sites are available for binding glycans. Both types of self-association can result in precipitates, as measured here by turbidometry and dynamic light scattering. Type-C self-association and precipitation occurred even with a galectin-3 mutant (R186S) that bound poorly to ASF, but required much higher concentration (~50μM) compared to wild type (~1μM). ASF also induced weaker type-C self-association of galectin-3 lacking its N-terminal part, but, as expected, no precipitation. Neither a monovalent or divalent LacNAc containing glycan induced type-C self-association, even if the latter gave precipitates with high concentrations of galectin-3 (> ~50μM) in agreement with published results, and perhaps due to type-N self-association.
|Research areas and keywords||
Subject classification (UKÄ) – MANDATORY
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 2012|
Related research output
Adriana Lepur, 2012, Department of Laboratory Medicine, Lund University. 71 p.
Research output: Thesis › Doctoral Thesis (compilation)