Fig. 3. PAR-3 generated in COS-7 cells associates with JAM-2 and JAM-3. Three T7 epitope-tagged PAR-3 constructs comprising either full-length PAR-3 (PAR-3/1-1337), or aa residues 583-1337 with the PDZ 3 and the aPKC binding domain (PAR-3/583-1337), or aa residues 258-936 with PDZ domains 1 to 3 and the aPKC binding domain (PAR-3/258-936) were transiently transfected into COS-7 cells. The lysates of transfected cells were incubated with immobilized GST-JAM fusion proteins and the resulting protein complexes were analysed by immunoblotting with antibodies against the T7 epitope. Arrowheads indicate the positions of recombinant PAR-3 molecules; the small arrow in the top right panel indicates PAR-3 degradation products. The two PAR-3 constructs containing PDZ domain 1 were efficiently affinity-isolated with both GST-JAM-2 and GST-JAM-3, whereas the construct lacking PDZ domains 1 and 2 did not bind to GST-JAM fusion proteins.