Scorpion neurotoxins: structure/function relationships and application in agriculture

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

Insecticidal activity of two proteases against Spodoptera frugiperda larvae infected with recombinant baculoviruses

“…Similar results were found with the introduction of the scorpion toxin AaIT gene from Androctonus australis with lethal time reduced by 25-40% when compared to wild-type virus [ 11 , 12 , 62 , 8 ]. Other toxins from scorpions [ 63 , 64 ], spiders [ 65 ], sea anemones [ 65 ] and B. thuringiensis [ 34 , 35 , 37 ] were also expressed using recombinant baculoviruses, and most of them showed an improvement on the virus speed of kill. Strong promoters as those in the transfer vector pSynXIVVI+X3 [ 49 , 51 ] are widely used for high levels of heterologous protein expression in insect cells.…”

Isolation and characterization of a novel type of neurotoxic peptide from the venom of the South African scorpion Parabuthus transvaalicus (Buthidae)

“…As summarized in the introduction identified potent peptides can be employed in the design and production of superior anti-venom. Also peptide toxins from scorpions are probes for identifying distinct types of ion channels and important tools for understanding their physiology [13,14]. One interesting feature of the venom of P. transvaalicus is its specialization towards mammalian activity, only one out of 10 initial fractions showed insect specificity.…”

Spider-Venom Peptides as Bioinsecticides

“…In particular, insecticidal toxins derived from insect predators and parasitoids are of growing interest in the development of bioinsecticides, and these include peptide neurotoxins derived from the venoms of scorpions [55], parasitic wasps [56], the straw itch mite [57], and spiders [58,59]. Currently, there is a great deal of interest in spider venoms as they comprise an extensive library of potent insecticidal, neurotoxic peptides.…”

“…The potential sources of biopesticides include microbes (viral, fungal, bacterial), entomophagous nematodes, plant-derived products, insect pheromones and insect resistance genes expressed in crops (for a review see reference [ 54 ]). In particular, insecticidal toxins derived from insect predators and parasitoids are of growing interest in the development of bioinsecticides, and these include peptide neurotoxins derived from the venoms of scorpions [ 55 ], parasitic wasps [ 56 ], the straw itch mite [ 57 ], and spiders [ 58 , 59 ]. Currently, there is a great deal of interest in spider venoms as they comprise an extensive library of potent insecticidal, neurotoxic peptides.…”