Usui et al. (2003)
found in yeast two-hybrid screening that an intracellular 349 amino acid fragment of plexin-B1 is interacting with plexin-A1. Furthermore, in a mammalian expression system Plexin-B1 physically associated with plexin-A1, but not with plexin-A2 or A3. They proposed that plexin-A1 and B1 interact in the adult brain and transduce Sema3A signaling in cooperation.