semar4dSemaphorin 4D (Sema4D) is a classic member of the semaphorin family involved in axonal guidance processes. The key effects of Sema4D in neurons are mediated by hh affinityRibbon diagrams of the seven-blade β propellers of (a) integrin αV (PDB code 1l5g), (b) SEMA3A (PDB code 1q47), (c) SEMA4D (PDB code 1olz) and (d) MET (PDB code 1shy). The