In this reaction, FGF receptor in the plasma membrane binds an associating extracellular ligand, a requisite step for subsequent activation. The resulting complex consists of dimerized receptor, two ligand molecules, and heparan sulfate. Also, TGFBR3 (beta-glycan) facilitates the binding of FGF2 with its receptor FGFR1 by binding with FGF2 itself and bringing more ligands into receptor proximity (Andres et al. 1992, Knelson et al. 2013).