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. 1999 Mar 30;96(7):3658–3663. doi: 10.1073/pnas.96.7.3658

Figure 6.

Figure 6

(a) Molecular model of the FGF–FGFR complex. FGF-2 molecule (Connolly surface rendering, colored in green) interacts with the Ig II and Ig III domains of the receptors. The Ig III domain of the receptor (bottom of the figure) interacts with the secondary binding site of FGF-2 (red) whereas the Ig II domain of FGFR interacts with the primary binding site of FGF-2 (purple). The Ig I domain of the receptor is not shown in this model. Notice that the linker between Ig II and Ig III is long and flexible to position the two Ig domains at diametrically opposite ends of the FGF-2 molecules. Extension of this model to the other members of the FGF family would suggest that the interaction at the primary site (purple and Ig II) would remain the same, whereas the interaction of the secondary site (Ig III and red) can vary to topologically other regions of the molecule. (b) A model of FGF-2–HLGAG–FGFR interaction. The HLGAG-binding site of FGF-2 is sandwiched between the primary and the secondary receptor-binding sites. HLGAG can bind to FGF-2 such that it interacts with both the receptor domains and the linker between the domains.