A stable oligomer of Bacillus thuringiensis delta-endotoxin, CryIIIA

Effects of Bacillus thuringiensis δ-Endotoxins on the Pea Aphid ( Acyrthosiphon pisum )

“…In two previous studies (10,11), sensitivity of another aphid, Macrosiphum euphorbiae, to suspensions of Cry2, Cry3A, and Cry4 crystals was reported but no sensitivity to solubilized endotoxins was found. This may be explained by the lack of complete solubilization of the Bt crystals (10) and by the fact that control groups were fed a water-based .…”

Identification, Isolation, and Cloning of a Bacillus thuringiensis CryIAc Toxin-binding Protein from the Midgut of the Lepidopteran Insect Heliothis virescens

“…The generally accepted model is that following toxin binding to a receptor protein or macromolecule, the toxin un- dergoes a conformational change that facilitates toxin insertion into the apical cell membrane of insect midgut columnar cells. This initial binding is then followed by oligomerization of the bound toxin (3,44,45). The cation ion selective pore formed by this oligomer causes a disruption of osmotic balance in the midgut epithelial layer (46 -48).…”

Single Molecule Fluorescence Study of the Bacillus thuringiensis Toxin Cry1Aa Reveals Tetramerization

“…Data on toxin aggregation or oligomerization in solution, i.e. before the toxin partitions into the membrane, are scarce and variable, ranging from monomers to oligomers with 8 -10 subunits (17)(18)(19)54). It was suggested that the toxin assembles into stable oligomer barrels (prepores) before inserting into the bilayer (43) but also that monomers insert into the bilayer first and subsequently diffuse laterally in the membrane to assemble into multimers to form pores (46,55,56).…”

“…In solution, B. thuringiensis toxin oligomers or aggregates of a large range of sizes have been observed (17)(18)(19). In receptor-free bilayers, a number of different B. thuringiensis toxins formed ion channels with principal conductances of several hundreds of picosiemens, but smaller conducting levels down to a few picosiemens were also observed, indicative of the presence of conducting substates, smaller size channels of a lower order of oligomerization, or both (7, 9, 20 -25).…”