| Abstract: | Continued use of non‐specific chemical insecticides poses potential risks to the environment and to human health resulting from non‐target toxicity and increased insect resistance to these agents. Scorpions produce anti‐insect selective polypeptide toxins that bind to and modulate voltage‐sensitive ion channels in excitable tissues, thus offering alternative, environmentally safer means for insect pest control. Despite this potential, little is known about their structural elements dictating anti‐insect preference, which may be useful for the design of selective insecticides. We used a bacterial system for expression and genetic dissection of two pharmacologically distinct scorpion toxins: alpha and excitatory. By exploiting a multi‐disciplinary approach consisting of mutagenesis, protein chemistry, electrophysiology, binding and toxicity assays, and structural studies, we elucidated the bioactive surface of two anti‐insect toxins, LqhαIT and Bj‐xtrIT. In both polypeptides the bioactive surface is composed of residues surrounding the C‐terminal region. In addition, a direct, immediate approach in using the toxin genes was demonstrated by engineering baculoviruses with cDNAs encoding LqhIT2 (depressant toxin), and LqhIT1 (excitatory toxin) resulting in viral vectors with significantly improved insecticidal efficacy. © 2000 Society of Chemical Industry |
