Characterization of the Novel Insecticidal Crystal Protein Cyt3Aa1 from <i>Bacillus thuringiensis</i> TD516

Bacillus thuringiensis (Bt) produces two families of insecticidal crystal proteins, i.e., crystalline (Cry) and cytolytic\r\n(Cyt) toxins. Cyt3Aa1, the newest Cyt family member, is produced by Bt TD516.\r\nBioassay results have shown that Cyt3Aa1 has weak hemolytic activity against\r\nhuman red blood cells and is not toxic to A. aegypti larvae, but causing a teratogenic effect. The three-dimensional\r\nstructure of Cyt3Aa1 has a typical cytolysin fold containing a β-sheet\r\nheld by two surrounding α-helical\r\nlayers, resembling the previously reported Cyt1Aa and Cyt2Aa structures, which\r\nindicated that Cyt3Aa1 might be a membrane-perforation toxin and could induce\r\nsynergism with Cry protein. This study provides a new source of insecticidal\r\ncrystal proteins, and presents a foundation for understanding the biological\r\ncharacterization of it, which will aid in the development of strategies to cope\r\nwith the potential problem of insect resistance.