Abstract
Human acidic fibroblast growth factors (aFGF-1) is a member of the fibroblast growth factor family which consists of at least 22 structurally related polypeptides with a wide range of physiological and pathological activities such as cell growth, differentiation, neovascularization and wound healing. Dimerization of the fibroblast growth factor receptor (FGFR) is proposed to be a key event in the transduction of the FGF-induced cellular signals. We have performed cell culture mitogenic assay to propose the mechanism of this biological activity. The ligand (SOS) we examined in this study was found to have mitogenic activity but can not dimerize FGF-1. We also apply a mutant hFGF-1 (C131D) which can not bind to heparin but, shows the mitogenic activity. The activity may not need to be induced by dimerization of FGF-1. The FGF-1 may be in a near-native state under physiological conditions and thus have the ability to transport its self across the membrane. nFGF-1 is a member of FGF-1 family. nFGF-1 is found to undergo heat-denature process with accumulation of late-intermediate at temperature around 60℃. Such an intermediate may further assemble to each other to form a superstructured amyloid fiber. With the performances of hydrogen-deuterium exchange experiments under acidic and neutral conditions, FGF-1 is found to be less stable in the acidic condition. This unstable species is found to interact with molecular chaperone-GroEL. GroEL recognizes the near-native state hFGF-1 in pH5.0 and unfolds it. Kinetic studies also indicate that GroEL can accelerate hFGF-1 refolding process under pH5.0 condition meaning that the refolding of hFGF-1 in acidic condition may via the accumulation of intermediate(s). Finally, we performed the H/D exchange experiments in the denatured hFGF-1. The results show that under 4 M urea and low pH (~4.5) condition, hFGF-1 possesses residual structures. These residual structures are mostly in sequential and hydrophobic. Besides, they are close to each other in the tertiary structure. They may be crucial to the initiation of protein folding.