title: Characterization of the heparin binding properties of annexin II tetramer.
abstract: In this report, we have characterized the interaction of heparin with the Ca2+- and phospholipid-binding protein annexin II tetramer (AIIt). Analysis of the circular dichroism spectra demonstrated that the Ca2+-dependent binding of AIIt to heparin caused a large decrease in the alpha-helical content of AIIt from approximately 44 to 31%, a small decrease in the beta-sheet content from approximately 27 to 24%, and an increase in the unordered structure from 20 to 29%. The binding of heparin also decreased the Ca2+ concentration required for a half-maximal conformational change in AIIt from 360 to 84 microM. AIIt bound to heparin with an apparent Kd of 32 +/- 6 nM (mean +/- S.D., n = 3) and a stoichiometry of 11 +/- 0.9 mol of AIIt/mol of heparin (mean +/- S.D., n = 3). The binding of heparin to AIIt was specific as other sulfated polysaccharides did not elicit a conformational change in AIIt. A region of the p36 subunit of AIIt (Phe306-Ser313) was found to contain a Cardin-Weintraub consensus sequence for glycosaminoglycan recognition. A peptide to this region underwent a conformational change upon heparin binding. Other annexins contained the Cardin-Weintraub consensus sequence, but did not undergo a substantial conformational change upon heparin binding.
authors.affiliation: Cell Regulation Research Group, Department of Medical Biochemistry, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
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: S L
authors.initials: SL
authors.lastname: Fitzpatrick
authors.forename: D M
authors.initials: DM
authors.lastname: Waisman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017306:Annexin A2 / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001704:Biopolymers; D002417:Cattle; D002942:Circular Dichroism; D006493:Heparin / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D017306:Annexin A2; D001704:Biopolymers; D006493:Heparin