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Fucoidan-dependent conformational changes in annexin II tetramer
S L Fitzpatrick1, G Kassam, A Manro
1Cancer Biology Research Group, Department of Medical Biochemistry, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Biochemistry
|March 1, 2000
Summary
Fucoidan, a sulfated polysaccharide, binds to annexin II tetramer (AIIt) independently of calcium. This interaction alters AIIt
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Fucoidan, a sulfated fucopolysaccharide, mimics cell surface glycans.
- Membrane polysaccharides play roles in cell-cell adhesion.
- Annexin II tetramer (AIIt) is a Ca(2+)- and phospholipid-binding protein.
Purpose of the Study:
- To characterize the interaction between fucoidan and annexin II tetramer (AIIt).
- To investigate the functional consequences of fucoidan binding to AIIt.
Main Methods:
- Biochemical assays to determine binding affinity (K(d)) and stoichiometry.
- Circular dichroism spectroscopy to assess conformational changes.
- Liposome binding and aggregation assays to evaluate functional effects.
Main Results:
- AIIt bound fucoidan with high affinity (K(d) ≈ 1.24 nM) in a Ca(2+)-independent manner.
- Fucoidan binding induced a significant decrease in AIIt's alpha-helical content, particularly in the presence of Ca(2+).
- Fucoidan binding to a specific peptide region of AIIt inhibited its ability to bind and aggregate phospholipid liposomes.
Conclusions:
- Fucoidan interacts directly with AIIt, suggesting a role for carbohydrate-protein interactions in cellular processes.
- The binding of fucoidan affects AIIt's structure and function, potentially modulating its role in membrane-related events.
- These findings highlight the impact of specific glycan-protein interactions on the biological activity of annexins.