The Vip3Ag4 insecticidal protoxin from bacillus thuringiensis adopts a tetrameric configuration that is maintained on proteolysis
2017
Palma Dovis, Leopoldo | Scott, David J. | Harris, Gemma | Din, Salah-Ud | Williams, Thomas L. | Roberts, Oliver J. | Young, Mark T. | Caballero Murillo, Primitivo | Berry, Colin | IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
The Vip3 proteins produced during vegetative growth by strains of the bacterium Bacillus thuringiensis show insecticidal activity against lepidopteran insects with a mechanism of action that may involve pore formation and apoptosis. These proteins are promising supplements to our arsenal of insecticidal proteins, but the molecular details of their activity are not understood. As a first step in the structural characterisation of these proteins, we have analysed their secondary structure and resolved the surface topology of a tetrameric complex of the Vip3Ag4 protein by transmission electron microscopy. Sites sensitive to proteolysis by trypsin are identified and the trypsin-cleaved protein appears to retain a similar structure as an octomeric complex comprising four copies each of the ~65 kDa and ~21 kDa products of proteolysis. This processed form of the toxin may represent the active toxin. The quality and monodispersity of the protein produced in this study make Vip3Ag4 a candidate for more detailed structural analysis using cryo-electron microscopy.
Show more [+] Less [-]The authors would like to thank the International Research Support Initiative Program Fellowship, Higher Education Commission of Pakistan for support to SUD. DJS is a Senior Molecular Biology and eutron Fellow supported by the Science and Technology Facilities Council (UK). GH is funded by the Medical Research Council (UK). Analytical services in the School of Chemistry, Cardiff University, were funded by EPSRC Grant number EP/L027240/1. Open access publishing was funded by Cardiff University.
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