title: The glycine box: a determinant of specificity for fibroblast growth factor.
abstract: Acidic fibroblast growth factor (FGF-1), keratinocyte growth factor (FGF-7), and FGF-10 are homologues with distinct specificity. In the presence of heparin, FGF-1 binds and activates in vitro all FGFR subtypes, while FGF-7 exhibits absolute specificity for the IIIb splice variant of FGFR2. FGF-10 exhibits a similar specificity but also binds the FGFR1IIIb isoform. Neither FGF-7 nor FGF-10 will bind to IIIc isoforms of FGFR. Molecular models of FGF, heparin, and the FGFR ectodomain suggested that sequences between beta-strands 10 and 12 of FGF may be important for the interaction of FGF with the heparin-FGFR ectodomain duplex. Site-directed mutants of FGF-7 and FGF-10 were prepared to test whether this domain might underlie failure of FGF-7 and FGF-10 to bind to the FGFRIIIc isoforms. Constructions with substitution of FGF-1 sequences spanning the entire C-terminus encoded in exon 3 or only C-terminal sequences spanning beta-strands 10 through 12 conferred ability on FGF-7 to bind to and activate FGFRIIIc without a significant loss in binding to or activation of FGFR2IIIb. A series of twelve different substitutions of shorter segments of FGF-1 sequences into the C-terminal portion of FGF-7 or FGF-10 revealed that substitution of GSCKRG for GIPVRG or the tri-peptide sequence KKN for NQK just N-terminal to it conferred dual activities on both the FGF-7 and FGF-10 backbones. The results suggest that the combined sequence domain, which we call the FGF glycine box (G-box), is a major determinant for the specificity of the binding of FGF to heparan sulfate-FGFR duplexes.
authors.affiliation: Center for Cancer Biology and Nutrition, Institute of Biosciences and Technology, Texas A&M University, Houston 77030-3303, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: W
authors.initials: W
authors.lastname: Lu
authors.forename: K A
authors.initials: KA
authors.lastname: Mohamedali
authors.forename: J H
authors.initials: JH
authors.lastname: Jang
authors.forename: R B
authors.initials: RB
authors.lastname: Jones
authors.forename: J L
authors.initials: JL
authors.lastname: Gabriel
authors.forename: M
authors.initials: M
authors.lastname: Kan
authors.forename: W L
authors.initials: WL
authors.lastname: McKeehan
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D004926:Escherichia coli / Q000235:genetics; D016220:Fibroblast Growth Factor 1; D051526:Fibroblast Growth Factor 10; D016222:Fibroblast Growth Factor 2 / Q000235:genetics; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005998:Glycine / Q000737:chemistry* / Q000378:metabolism; D006133:Growth Substances / Q000235:genetics; D006493:Heparin / Q000378:metabolism; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D051381:Rats; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000138:chemical synthesis / Q000302:isolation & purification; D018411:Spodoptera / Q000235:genetics
chemical_list: C496463:FGF10 protein, human; C496453:FGF7 protein, human; C496464:Fgf10 protein, mouse; C496465:Fgf10 protein, rat; C496454:Fgf7 protein, mouse; C496455:Fgf7 protein, rat; D051526:Fibroblast Growth Factor 10; D006133:Growth Substances; D010446:Peptide Fragments; D017468:Receptors, Fibroblast Growth Factor; D011993:Recombinant Fusion Proteins; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D006493:Heparin; D005998:Glycine