Insecticidal toxin complex proteins from Xenorhabdus nematophilus: Structure and pore formation
28.04.2011
Sheets JJ, Hey TD, Fencil KJ, Burton SL, Ni W, Lang AE, Benz R, Aktories K.
J Biol Chem. 2011;286(26):22742-9.
Toxin complexes from Xenorhabdus or Photorhabdus spp. bacteria represent novel insecticidal proteins. We have 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 show 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 binds to solubilized insect brush border membranes, and induces 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-terminal cleaved portion of XptC1 apparently only loosely associates with this binary complex. XptA2 has only modest oral toxicity against lepidopteran insects, but as a complex with co-produced XptB1 and XptC1 has 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 results 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, is highly active against insects.
