A COMPARISON OF THE CONFORMATION OF SUCROSE OCTASULFATE, FREE AND BOUND TO ACIDIC FIBROBLAST GROWTH-FACTOR

The conformation of sucrose octasulfate free in solution has been determined based on high-resolution NMR spectroscopy. Three-bond H-1-H-1 scalar coupling constants, laboratory and rotating frame NOEs, long-range H-1-C-13 scaIar coupling constants, and chemical-shift temperature and ionic-strength dependence were used, aided by molecular mechanics calculations. By modification of a pulse sequence designed for measuring long-range H-1-C-13 coupling constants, it was possible to obtain an accurate value for the (3)J(C2f-H1g) despite the confounding presence of (3)J(HH) of similar value. Free sucrose octasulfate appears to assume a conformation significantly different from any of the eight conformations observed bound to acidic fibroblast growth factor, as determined in a previous X-ray crystallographic study [X. Zhu, B.T. Hsu, and D.C. Rees, Structure, 1 (1993) 27-34]. Strong electrostatic interactions between guest and host may be the dominant factor in deformation of sucrose octasulfate. The implications of this study for protein-carbohydrate interactions and the effects of the presence of sulfate groups on the flexibility of sucrose are also discussed.