the N-terminal region of the primary amino acid sequence whereas regions from throughout the protein sequence contribute to the head domain in Etx/Mtx2 toxins. In addition, the head domains of the Toxin_10 proteins show lectin-like features of carbohydrate binding domains. The only reported natural targets of Toxin_10 proteins are insects. With the exception of Cry36 and Cry78, the Toxin_10 toxins appear to act as two-part, binary toxins. The partner proteins in these combinations may belong to different structural groups, depending on the individual toxin: two Toxin_10 proteins (BinA and BinB) act together in the Bin mosquitocidal toxin of Lysinibacillus sphaericus; the Toxin_10 Cry49 is co-dependent on the 3-domain toxin family member Cry48 for its activity against Culex mosquito larvae; and the Bacillus thuringiensis Toxin_10 protein Cry35 interacts with the aegerolysin family Cry34 to kill Western Corn Rootworm. This toxin pair has been included in insect resistant plants such as SmartStax corn. Mode of action β-PFTs are dimorphic proteins that exist as soluble monomers and then assemble to form multimeric assemblies that constitute the pore. Figure 1 shows the pore-form of α-Hemolysin, the first crystal structure of a β-PFT in its pore-form. 7 α-Hemolysin monomers come together to create the mushroom-shaped pore. The 'cap' of the mushroom sits on the surface of the cell, and the 'stalk' of the mushroom penetrates the cell membrane, rendering it permeable (see later). The 'stalk' is composed of a 14-strand β-barrel, with two strands donated from each monomer. A structure of the Vibrio cholerae cytolysin in the pore form is also heptameric; however, Staphylococcus aureus gamma-hemolysin reveals an octomeric pore, consequently with a 16-strand 'stalk'. The Panton-Valentine leucocidin S structure shows a highly related structure, but in its soluble monomeric state. This shows that the strands involved in forming the 'stalk' are in a very different conformation – shown in Fig 2. Structural comparison of pore-form α-Hemolysin (pink/red) and soluble-form PVL (pale green/green). It is postulated that the green section in PVL 'flips out' to the 'red' conformation as seen in α-Haemolysin. (PDB: 7AHL, 1T5R) β-PFTs are dimorphic proteins that exist as soluble monomers and then assemble to form multimeric assemblies that constitute the pore. Figure 1 shows the pore-form of α-Hemolysin, the first crystal structure of a β-PFT in its pore-form. 7 α-Hemolysin monomers come together to create the mushroom-shaped pore. The 'cap' of the mushroom sits on the surface of the cell, and