Crystal structure of the Flt3_D1-D4:FL complex. (A) Domain organization of the Flt3 extracellular segment. The 5 Ig-like domains of Flt3 (D1, residues 79-161; D2, residues 167-244; D3, residues 245-345; D4, residues 348-434; and D5, residues 435-533) are shown as colored boxes. The N-linked glycosylation sites are indicated with blue diamonds. Partially occupied glycosylation sites are indicated with an asterisk (*). Also shown is the disulfide bond network in Flt3_D1-D4 as determined by mass spectrometry. The putative disulfide bridges in Flt3_D5 are shown as dashed lines, based on homology with Flt3_D2 and KIT_D5. (B) Overall structure of the Flt3_D1-D4:FL complex. The crystal structure of the Flt3_D1-D4:FL complex is shown in ribbon representation with the 2-fold symmetry axis of FL oriented along the vertical axis of the plane. Flt3 domains follow the coloring scheme in panel A. Disulfide bridges are shown as yellow spheres, and N-linked glycans as green sticks. The structural panels to the right show 2 alternative views of the complex with FL in ribbon representation and the receptor in surface representation.