Left panels. The structures of the N-terminal regions from Drosophila Delta (A) and Serrate (B) are shown in a cartoon representation (rainbow coloured from blue at N-terminus to red at C-terminus). These have been overlaid on their mammalian equivalents DLL-4 (A) and Jagged-1 (B) in the context of their complexes (PDB entries 4xlw and 5uk5 respectively) with Notch-1 (cartoon representation, coloured grey). The structure of isolated Drosophila Notch is also depicted in each panel (cartoon, rainbow coloured) superposed on the respective copy of mammalian Notch-1 (cartoon, grey) for each complex. The overlays demonstrate the high degree of conservation in domain structures and arrangements between the Drosophila and mammalian homologues. Right panels. A close-up view of the C2 domains of each ligand overlaid with their mammalian equivalent. These demonstrate conservation of overall fold but large differences in the apical loops, particularly in the β1-2 and β5-6 loops. 