4 research outputs found
The amino- and carboxyl-terminal fragments of the Bacillus thuringensis Cyt1Aa toxin have differential roles on toxin oligomerization and pore formation
The Cyt toxins produced by the bacteria Bacillus thuringiensis show insecticidal activity against
some insects, mainly dipteran larvae, being able to kill mosquitoes and black flies. However, they
also possess a general cytolytic activity in vitro showing hemolytic activity in red blood cells.
These proteins are composed of two outer layers of α-helix hairpins wrapped around a β-sheet.
Regarding to their mode of action, one model proposed that the two outer layers of α-helix
hairpins swing away from the β-sheet allowing insertion of β-strands into the membrane forming a
pore after toxin oligomerization. The other model suggested a detergent-like mechanism of action
of the toxin on the surface of the lipid bilayer. In this work we cloned the N- and C-terminal
domains form Cyt1Aa and analyzed their effects in Cyt1Aa toxin action. The N-terminal domain
shows a dominant negative phenotype inhibiting the in vitro hemolytic activity of Cyt1Aa in red
blood cells and the in vivo insecticidal activity of Cyt1Aa against Aedes aegypti larvae. In
addition, N-terminal region is able to induce aggregation of Cyt1Aa toxin in solution. Finally, Cterminal
domain composed mainly of β-strands, is able to bind to the SUV liposomes, suggesting
that this region of the toxin is involved in membrane interaction. Overall, our data indicate that the
two isolated domains of Cyt1Aa have different roles in toxin action. The N-terminal region is
involved in toxin aggregation while the C-terminal domain in the interaction of the toxin with the
lipid membrane.Research was funded in part through grants from the National Institutes of Health, 1R01
AI066014, DGAPA/UNAM IN218608 and IN210208-N, CONACyT U48631-Q 478. IRdE received a José
Castillejo postdoctoral grant, and a mobility grant for teaching and research staff of UPNA, Spain