Investigation of the structural stability of the human acidic fibroblast growth factor by hydrogen-deuterium exchange.

The conformational stability of the human acidic fibroblast growth factor (hFGF-1) is investigated using amide proton exchange and temperature-dependent chemical shifts, monitored by two-dimensional NMR spectroscopy. The change in free energy of unfolding (ΔGu) of hFGF-1 is estimated to be 5.00 ± 0.09 kcal·mol-1. Amide proton-exchange rates of 74 residues (in hFGF-1) have been unambiguously measured, and the exchange process occurs predominately according to the conditions of the EX2 limit. The exchange rates of the fast-exchanging amide protons exposed to the solvent have been measured using the clean SEA-HSQC technique. The amide proton protection factor and temperature coefficient estimates show reasonably good correlation. Residues in β-strands II and VI appear to constitute the stability core of the protein. Among the 12 β-strands constituting the β-barrel architecture of hFGF-1, β-strand XI, located in the heparin binding domain, exhibits the lowest average protection factor value. Amide protons inv...