PMID: 20727575 , Related PDB ids: 3NVN, 3NVQ, 3NVX

Authors:

Liu H, Juo ZS, Shim AH, Focia PJ, Chen X, Garcia KC, He X

Title:

Structural basis of semaphorin-plexin recognition and viral mimicry from Sema7A and A39R complexes with PlexinC1.

Journal:

Cell. 2010 Sep 3;142(5):749-61. Epub 2010 Aug 19.

Abstract:

Repulsive signaling by Semaphorins and Plexins is crucial for the development and homeostasis of the nervous, immune, and cardiovascular systems. Sema7A acts as both an immune and a neural Semaphorin through PlexinC1, and A39R is a Sema7A mimic secreted by smallpox virus. We report the structures of Sema7A and A39R complexed with the Semaphorin-binding module of PlexinC1. Both structures show two PlexinC1 molecules symmetrically bridged by Semaphorin dimers, in which the Semaphorin and PlexinC1 beta propellers interact in an edge-on, orthogonal orientation. Both binding interfaces are dominated by the insertion of the Semaphorin's 4c-4d loop into a deep groove in blade 3 of the PlexinC1 propeller. A39R appears to achieve Sema7A mimicry by preserving key Plexin-binding determinants seen in the mammalian Sema7A complex that have evolved to achieve higher affinity binding to the host-derived PlexinC1. The complex structures support a conserved Semaphorin-Plexin recognition mode and suggest that Plexins are activated by dimerization.