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Ligand induced galectin-3 self-association.

In English

Författare

Summary, in English

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.

Avdelning/ar

Publiceringsår

2012

Språk

Engelska

Sidor

21751-21756

Publikation/Tidskrift/Serie

Journal of Biological Chemistry

Volym

287

Issue

26

Dokumenttyp

Artikel i tidskrift

Förlag

American Society for Biochemistry and Molecular Biology

Ämne

  • Microbiology in the medical area
  • Immunology in the medical area

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1083-351X