Bri2 and Bri3 architecture and antibody reactivity. A) SDS-PAGE and Coomassie staining of recombinant Bri2 BRICHOS (residues 113–231) (left) and Bri3 BRICHOS (residues 112–230) (right) domains. The lines to the left show migration of size markers with masses in kDa. B) Bri2 and Bri3 are characterized by a similar architecture: an intracellular domain (IC) (yellow), a transmembrane (TM) region (green), a linker region (light blue), the BRICHOS domain (red) and a C-terminal segment (Bri23 or CT, blue). The sequence positions of the different domains in Bri2 and Bri3, respectively, are indicated. Antibodies, used in this study, were raised against the indicated segments of Bri2 and Bri3. C) Western blots of recombinant Bri2 and Bri3 BRICHOS proteins (corresponding to residues 113–231 of Bri2, residues 90–236 of Bri2 and residues 112–230 of Bri3) using the anti-Bri2 linker; the anti-Bri2 BRICHOS; and the anti-Bri3 BRICHOS antibodies. The upper band for Bri2 BRICHOS (113-231) corresponds to a dimer. Size markers (kDa) are shown to the right of the blots.