Figure 5

Crystal structures of the mouse CNTN5–APP complex and chicken CNTN3–APP fusion protein.A, the crystal structure of mouse APP(E1) bound to the FN1–FN3 region of mouse CNTN5 is shown in coil representation along with a translucent surface. B, detailed view of side chain–side chain interactions at the CNTN5–APP interface. Dashed lines indicate potential hydrogen bonds or salt bridges, whereas translucent surfaces highlight residues involved in packing interactions. C, main chain–main chain and side chain–main chain hydrogen bonding network, indicated by dashed lines, between antiparallel β-strands in CNTN5 and APP. Side chains not involved in contacts are removed for clarity. In B and C, corresponding residues at the CNTN4–APP interface are superimposed and shown in white. The structures were superimposed using the copper-binding domains of APP (RMSD of 0.46 Å over 69 Cα pairs). D, the crystal structure of the fusion protein between the FN1–FN2 region of chicken CNTN3 fused to the E1 domain of chicken APP is shown in coil and surface representations. E, detailed view of side chain–side chain interactions at the CNTN3–APP interface. Dashed lines indicate potential hydrogen bonds or salt bridges, whereas translucent surfaces highlight residues involved in packing interactions. F, main chain–main chain and side chain–main chain hydrogen bonding network, indicated by dashed lines, between antiparallel β-strands in CNTN3 and APP. Side chains not involved in contacts are removed for clarity. In E and F, corresponding residues at the CNTN4–APP interface are superimposed and shown in white. The structures were superimposed using the copper-binding domains of APP (RMSD of 0.25 Å over 69 Cα pairs). APP, amyloid precursor protein; CNTN3, contactin 3; CNTN5, contactin 5; FN1, first FN repeat; FN2, second FN repeat; FN3, third FN repeat.