Conformational Flexibility of a Synthetic Glycosylaminoglycan Bound to a Fibroblast Growth Factor. FGF-1 Recognizes Both the 1C4 and 2SO Conformations of a Bioactive Heparin-like Hexasaccharide

The first direct NMR determination of the conformation of a conformationally flexible heparin-like hexasaccharide bound to a key receptor, FGF-1, is described. The determination has been based on the use of a 13C-labeled protein and a regular 12C sugar. FGF-1 recognizes several conformations of the iduronic moieties of the hexasaccharide. Therefore, this case is different than that described for the controversial recognition of heparin-like saccharides by AT-III, which seems to recognize just one conformation of the iduronic acid residues.