ATP-binding on fibroblast growth factor 2 partially overlaps with the heparin-binding domain.

Fibroblast growth factor 2 (FGF2), an intensively studied heparin-binding cytokine, is an important modulator of cell growth and differentiation under both physiological and pathophysiological conditions. It has been shown recently that ATP binds to FGF2 and that this binding is crucial for its biological function. In this study we demonstrated that divalent cations were not necessary for binding of ATP to FGF2, but it could be demonstrated that heparin blocked the labelling of FGF2 with ATP indicating an involvement of the heparin-binding domain (aa 128-144) in ATP-binding. FGF2, bound to Heparin Sepharose, could be eluted with ATP and GTP, but not with cAMP, AMP or ADP. Successive mutation of positively charged amino acid residues located in the heparin-binding domain drastically reduced the signal intensity of [gamma-(32)P]ATP labelled FGF2 indicating that this domain is not only important for heparin binding to FGF2 but also for ATP-binding.