Complex effects of molecular chaperones on the aggregation and refolding of fibroblast growth factor-1

Fibroblast growth factor one (FGF-1) exists in a molten globule (MG)-like s tate under physiological conditions (neutral pH, 37 degreesC). It has been proposed that this form of the protein may be involved in its atypical memb rane transport properties. Macromolecular chaperones have been shown to bin d to MG states of proteins as well as to be involved in protein membrane tr ansport. We have therefore examined the effect of such proteins on the aggr egation and refolding of FGF-1 to evaluate whether they might play a role i n FGF-1 transport. The proposed chaperone alpha -crystallin was found to st rongly inhibit the aggregation of the MG state of FGF-1. Curiously, two oth er proteins of similar size and charge (thyroglobulin and a monoclonal IgM immunoglobulin) with no previously reported chaperone properties were also found to have a related effect. In contrast, the chaperone GroEL/ES induced further aggregation of MG-like FGF-1 but had no effect on the native confo rmation. Both chaperones stimulated refolding to the native state (25 degre esC) but had no detectable effect when FGF-1 was refolded to the MG state ( 37 degreesC). This suggests that disordered intermediates are present in th e folding pathways of the native and MG-like FGF conformations which differ from the MG-like state induced under physiological conditions. FGF-1 does, therefore, interact with molecular chaperones, although this may involve b oth the MG and the native states of the protein. (C) 2001 Academic Press.