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Toxins 2017, 9(5), 165; doi:10.3390/toxins9050165

The Vip3Ag4 Insecticidal Protoxin from Bacillus thuringiensis Adopts A Tetrameric Configuration That Is Maintained on Proteolysis

Instituto de Agrobiotecnología, CSIC-UPNA-Gobierno de Navarra, Campus Arrosadía, Mutilva 31192, Navarra, Spain
School of Biosciences, University of Nottingham, Sutton Bonnington Campus, Leicestershire LE12 5RD, UK
Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Oxfordshire OX11 0FA, UK
ISIS Spallation Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Oxfordshire OX11 0QX, UK
Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK
Cardiff School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK
Current address: Centro de Investigaciones y Transferencia de Villa María (CITVM-CONICET), Universidad Nacional de Villa María, Villa María, Córdoba 5900, Argentina.
Current address: National Center of Excellence in Molecular Biology (CEMB), University of the Punjab, Lahore P.O. Box No. 54590, Pakistan.
Author to whom correspondence should be addressed.
Academic Editor: Shin-ichi Miyoshi
Received: 17 January 2017 / Revised: 11 May 2017 / Accepted: 12 May 2017 / Published: 14 May 2017
(This article belongs to the Special Issue Cellular Entry of Binary and Pore-Forming Bacterial Toxins)
View Full-Text   |   Download PDF [3160 KB, uploaded 31 May 2017]   |  


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. View Full-Text
Keywords: Vip3 toxin; electron microscopy; surface topology Vip3 toxin; electron microscopy; surface topology

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Palma, L.; Scott, D.J.; Harris, G.; Din, S.-U.; Williams, T.L.; Roberts, O.J.; Young, M.T.; Caballero, P.; Berry, C. The Vip3Ag4 Insecticidal Protoxin from Bacillus thuringiensis Adopts A Tetrameric Configuration That Is Maintained on Proteolysis. Toxins 2017, 9, 165.

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