title: Fucoidan-dependent conformational changes in annexin II tetramer.
abstract: Fucoidan, a sulfated fucopolysaccharide, mimics the fucosylated glycans of glycoproteins and has therefore been used as a probe for investigating the role of membrane polysaccharides in cell-cell adhesion. In the present report we have characterized the interaction of fucoidan with the Ca(2+)- and phospholipid-binding protein annexin II tetramer (AIIt). AIIt bound to fucoidan with an apparent K(d) of 1.24 +/- 0.69 nM (mean +/- SD, n = 3) with a stoichiometry of 0.010 +/- 0.001 mol of fucoidan/mol of AIIt (mean +/- SD, n = 3). The binding of fucoidan to AIIt was Ca(2+)-independent. Furthermore, in the presence but not the absence of Ca(2+), the binding of fucoidan to AIIt caused a decrease in the alpha-helical content from 32% to 7%. A peptide corresponding to a region of the p36 subunit of AIIt, F(306)-S(313), which contains a Cardin-Weintraub consensus sequence for heparin binding, was shown to undergo a conformational change upon fucoidan binding. This suggests that heparin and fucoidan bound to this region of AIIt. The binding of fucoidan but not heparin by AIIt also inhibited the ability of AIIt to bind to and aggregate phospholipid liposomes. These results suggest that the binding of AIIt to the carbohydrate conjugates of certain membrane glycoproteins may have profound effects on the structure and biological activity of AIIt.
authors.affiliation: Cancer Biology Research Group, Department of Medical Biochemistry, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: S L
authors.initials: SL
authors.lastname: Fitzpatrick
authors.forename: G
authors.initials: G
authors.lastname: Kassam
authors.forename: A
authors.initials: A
authors.lastname: Manro
authors.forename: C E
authors.initials: CE
authors.lastname: Braat
authors.forename: P
authors.initials: P
authors.lastname: Louie
authors.forename: D M
authors.initials: DM
authors.lastname: Waisman
mesh_terms: D000595:Amino Acid Sequence; D017306:Annexin A2 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D005643:Fucose / Q000737:chemistry; D006493:Heparin / Q000737:chemistry; D008081:Liposomes / Q000037:antagonists & inhibitors / Q000737:chemistry; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D012624:Seaweed; D013463:Sulfuric Acid Esters / Q000737:chemistry
chemical_list: D017306:Annexin A2; D008081:Liposomes; D011134:Polysaccharides; D013463:Sulfuric Acid Esters; D005643:Fucose; D006493:Heparin; C007789:fucoidan; D002118:Calcium