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FGF domain, beta-trefoil fold, found in acidic and basic fibroblast growth factor (FGF) superfamily The FGF superfamily includes FGF1-23 and similar proteins. FGFs are mitogens, which stimulate growth or differentiation of cells of mesodermal or neuroectodermal origin. They play essential roles in patterning and differentiation during vertebrate embryogenesis and have neurotrophic activities. FGFs have a high affinity for heparan sulfate proteoglycans and require heparan sulfate to activate one of four cell surface FGF receptors. Upon binding to FGF, the receptors dimerize, and their intracellular tyrosine kinase domains become active. The structure of FGFs is typical of the beta-trefoil fold, which is characterized by 12 beta strands folded into three similar trefoil subdomains (alpha, beta, and gamma) associated to give an overall structure with pseudo-3-fold symmetry.
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