FGF domain, beta-trefoil fold, found in fibroblast growth factor 23 (FGF23) and similar proteins
FGF23, also called phosphatonin, or tumor-derived hypophosphatemia-inducing factor (HYPF), is a regulator of phosphate homeostasis. It inhibits renal tubular phosphate transport by reducing SLC34A1 levels. It upregulates EGR1 expression in the presence of alpha-Klotho (KL). It acts directly on the parathyroid to decrease PTH secretion. FGF23 acts as a regulator of vitamin-D metabolism. It negatively regulates osteoblast differentiation and matrix mineralization. FGF23 interacts with fibroblast growth factor receptors, FGFR1, FGFR2, FGFR3, and FGFR4. Affinity between fibroblast growth factors (FGFs) and their receptors is increased by KL and heparan sulfate glycosaminoglycans that function as coreceptors. FGF23 contains a FGF domain with 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",