Mapping ligand binding domains in chimeric fibroblast growth factor receptor molecules. Multiple regions determine ligand binding specificity.
Fibroblast growth factors (FGFs) mediate essential cellular functions by activating one of four alternatively spliced FGF receptors (FGFRs). To determine the mechanism regulating ligand binding affinity and specificity, soluble FGFR1 and FGFR3 binding domains were compared for activity. FGFR1 bound well to FGF2 but poorly to FGF8 and FGF9. In contrast, FGFR3 bound well to FGF8 and FGF9 but poorly to FGF2. The differential ligand binding specificity of these two receptors was exploited to map specific ligand binding regions in mutant and chimeric receptor molecules. Deletion of immunoglobulin-like (Ig) domain I did not effect ligand binding, thus localizing the binding region(s) to the distal two Ig domains. Mapping studies identified two regions that contribute to FGF binding. Additionally, FGF2 binding showed positive cooperativity, suggesting the presence of two binding sites on a single FGFR or two interacting sites on an FGFR dimer. Analysis of FGF8 and FGF9 binding to chimeric receptors showed that a broad region spanning Ig domain II and sequences further N-terminal determines binding specificity for these ligands. These data demonstrate that multiple regions of the FGFR regulate ligand binding specificity and that these regions are distinct with respect to different members of the FGF family.
Chellaiah
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Department of Molecular Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Yuan
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Chellaiah
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Ornitz
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D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D019556:COS Cells; D005346:Fibroblast Growth Factors / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D017354:Point Mutation; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051497:Receptor, Fibroblast Growth Factor, Type 2; D051498:Receptor, Fibroblast Growth Factor, Type 3; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D017468:Receptors, Fibroblast Growth Factor; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D005346:Fibroblast Growth Factors; C496348:FGFR1 protein, human; C496353:FGFR2 protein, human; C496365:FGFR3 protein, human; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051497:Receptor, Fibroblast Growth Factor, Type 2; D051498:Receptor, Fibroblast Growth Factor, Type 3