Insecticidal Toxin Complex Proteins from Xenorhabdus nematophilus

• Published in: The Journal of biological chemistry 2011-07, Vol.286 (26), p.22742-22749
• Main Authors: Sheets, Joel J., Hey, Tim D., Fencil, Kristin J., Burton, Stephanie L., Ni, Weiting, Lang, Alexander E., Benz, Roland, Aktories, Klaus
• Format: Article
• Language: English
• Subjects: Insect; Membrane Bilayer; Protein Assembly; Protein Self-assembly; Protein-Protein Interactions; Receptors; Toxins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.227009

Toxin complexes from Xenorhabdus and Photorhabdus spp. bacteria represent novel insecticidal proteins. We purified a native toxin complex (toxin complex 1) from Xenorhabdus nematophilus. The toxin complex is composed of three different proteins, XptA2, XptB1, and XptC1, representing products from class A, B, and C toxin complex genes, respectively. We showed that recombinant XptA2 and co-produced recombinant XptB1 and XptC1 bind together with a 4:1:1 stoichiometry. XptA2 forms a tetramer of ∼1,120 kDa that bound to solubilized insect brush border membranes and induced pore formation in black lipid membranes. Co-expressed XptB1 and XptC1 form a tight 1:1 binary complex where XptC1 is C-terminally truncated, resulting in a 77-kDa protein. The ∼30-kDa C-terminally cleaved portion of XptC1 apparently only loosely associates with this binary complex. XptA2 had only modest oral toxicity against lepidopteran insects but as a complex with co-produced XptB1 and XptC1 had high levels of insecticidal activity. Addition of co-expressed class B (TcdB2) and class C (TccC3) proteins from Photorhabdus luminescens to the Xenorhabdus XptA2 protein resulted in formation of a hybrid toxin complex protein with the same 4:1:1 stoichiometry as the native Xenorhabdus toxin complex 1. This hybrid toxin complex, like the native toxin complex, was highly active against insects.