Features of I12 Bowman-Birk peptidase inhibitors. (A) Three-dimensional structure of typical I12 inhibitors with one domain (1BBI) or two domains (2FJ8). Cysteines are highlighted as balls and sticks and coloured in CPK. Yellow, β-sheets. (B) Schematic PhyML phylogenetic tree using the selected Bowman-Birk sequences from the different plant species. Coloured triangles show clade-specific gene proliferations.