Molecular basis for the Kallmann syndrome-linked fibroblast growth factor receptor mutation

► The structural basis of the Kallmann syndrome is elucidated. ► Kallmann syndrome mutation (A168S) induces a subtle conformational change(s). ► Structural interactions mediated by beta-sheet G are most perturbed. ► Ligand (FGF)-receptor interaction(s) is completely abolished by Kallmann mutation. ► Kallmann mutation directly affects the FGF signaling process.