title: Conformation of heparin pentasaccharide bound to antithrombin III.
abstract: The interaction, in aqueous solution, of the synthetic pentasaccharide AGA*IA(M) (GlcN,6-SO(3)alpha 1-4GlcA beta 1-4GlcN,3,6-SO(3)alpha 1-4IdoA,2-SO(3)alpha 1-4GlcN,6-SO(3)alpha OMe; where GlcN,6-SO(3) is 2-deoxy-2-sulphamino-alpha-D-glucopyranosyl 6-sulphate, IdoA is l-iduronic acid and IdoA2-SO(3) is L-iduronic acid 2-sulphate), which exactly reproduces the structure of the specific binding sequence of heparin and heparan sulphate for antithrombin III, has been studied by NMR. In the presence of antithrombin there were marked changes in the chemical shifts and nuclear Overhauser effects (NOEs), compared with the free state. On the basis of the optimized geometry of the pentasaccharide the transferred NOEs were interpreted with full relaxation and conformational exchange matrix analysis. An analysis of the three-dimensional structures of the pentasaccharide in the free state, and in the complex, revealed the binding to be accompanied by dihedral angle variation at the A-G and I-A(M) (where G, I, A and A(M) are beta-d-glucuronic acid, 2-O-sulphated alpha-L-iduronic acid, N,6-O-sulphated alpha-D-glucosamine and the alpha-methyl-glycoside of A respectively) glycosidic linkages. Evidence is also provided that the protein drives the conformation of the 2-O-sulphated iduronic acid residue towards the skewed (2)S(0) form.
authors.affiliation: Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 842 38 Bratislava, Slovakia. hricovini@savbk.sk
authors.forename: M
authors.initials: M
authors.lastname: Hricovíni
authors.forename: M
authors.initials: M
authors.lastname: Guerrini
authors.forename: A
authors.initials: A
authors.lastname: Bisio
authors.forename: G
authors.initials: G
authors.lastname: Torri
authors.forename: M
authors.initials: M
authors.lastname: Petitou
authors.forename: B
authors.initials: B
authors.lastname: Casu
mesh_terms: D000990:Antithrombin III / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006493:Heparin / Q000737:chemistry* / Q000378:metabolism*; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012996:Solutions
chemical_list: D046911:Macromolecular Substances; D009844:Oligosaccharides; D012996:Solutions; C049714:IC 831423; D000990:Antithrombin III; D006493:Heparin