| Using the cytoplasmic domain of fibroblast growth factor receptor 1 ( FGFR 1 ) as bait in a yeast two hybrid screen , Grb 14 was identified as a FGFR 1 binding partner . ^^^ A kinase inactive mutant of FGFR 1 failed to interact with Grb 14 , indicating that activation of FGFR 1 is necessary for binding . ^^^ Deletion of the C tail or mutation of both C tail tyrosine residues of FGFR 1 to phenylalanine abolished binding , and deletion of the juxtamembrane domain of the receptor reduced binding , suggesting that Grb 14 binds to FGFR 1 at multiple sites . ^^^ Co immunoprecipitation and in vitro binding assays demonstrated that binding of Grb 14 to FGFR 1 in mammalian cells was dependent on receptor activation by fibroblast growth factor 2 ( FGF 2 ) . ^^^ Deletion of the Src homology 2 ( SH 2 ) domain of Grb 14 reduced but did not block binding to FGFR 1 and eliminated dependence on receptor activation . ^^^ |