Figure 1. The semaphorin–plexin complexes share a common architecture.

a, Schematic domain organization of human PLXNB1, mouse PlxnA2, human SEMA4D and mouse Sema6A. PLXNB1 contains an additional mucin-like domain inserted into the PSI2 domain. SP, signal peptide; TM, transmembrane. The domains included in the crystallization constructs are coloured. b, Ribbon representation of PlxnA2_1–4 ‘rainbow’ colour ramped from blue (N terminus) to red (C terminus) with the β-propeller blades numbered. N-linked glycans are shown in magenta ball-and-stick representation and the 14 disulphide bridges (black stick presentation) are marked with Roman numbering. c, Multi-angle light scattering indicates an experimental molecular mass (black line) of 83.7 ± 0.8 kDa for PlxnA2_1–4 (green line; elution profile, axis not shown) as observed by SDS–PAGE (inset) and in agreement with the theoretical molecular mass for a monomer (85 kDa). d, Ribbon representation (left panel), cartoon drawing (middle panel) and surface representations with individual protein chains indicated by an outline (right panel) of the PLXNB1_1–2–SEMA4D_ecto and PlxnA2_1–4–Sema6A_ecto complexes. Domains are coloured as in Fig. 1a.