Comparison of representative RTKIII/V extracellular complexes. The structures shown represent the architecture of receptor-cytokine complexes for the different members of the RTKIII/V family: From left to right: human Flt3:FL (this study), human KIT:SCF (PDB 2E9W), mouse CSF-1R:CSF-1 (PDB 3EJJ), human platelet-derived growth factor receptor:platelet-derived growth factor (PDGFR:PDGF; PDB 3MJG), and human VEGFR2:VEGF (PDB 2X1X). The dimeric ligands are colored in magenta. Receptor ectodomains are colored as follows: D1 in pale yellow, D2 in blue, D3 in green, D4 in orange, and D5 in gray.