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Toxins (Basel). 2017 May 14;9(5). pii: E165. doi: 10.3390/toxins9050165.

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

Author information

1
Instituto de Agrobiotecnología, CSIC-UPNA-Gobierno de Navarra, Campus Arrosadía, Mutilva 31192, Navarra, Spain. lpalma.leopoldo@gmail.com.
2
School of Biosciences, University of Nottingham, Sutton Bonnington Campus, Leicestershire LE12 5RD, UK. david.scott@nottingham.ac.uk.
3
Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Oxfordshire OX11 0FA, UK. david.scott@nottingham.ac.uk.
4
ISIS Spallation Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Oxfordshire OX11 0QX, UK. david.scott@nottingham.ac.uk.
5
Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Oxfordshire OX11 0FA, UK. gemma.harris@rc-harwell.ac.uk.
6
Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK. salahuddin@cemb.edu.pk.
7
Cardiff School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK. williamst30@cardiff.ac.uk.
8
Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK. o.roberts1@nhs.net.
9
Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK. youngmt@cardiff.ac.uk.
10
Instituto de Agrobiotecnología, CSIC-UPNA-Gobierno de Navarra, Campus Arrosadía, Mutilva 31192, Navarra, Spain. pcm92@unavarra.es.
11
Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK. berry@cardiff.ac.uk.

Abstract

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.

KEYWORDS:

Vip3 toxin; electron microscopy; surface topology

PMID:
28505109
PMCID:
PMC5450713
DOI:
10.3390/toxins9050165
[Indexed for MEDLINE]
Free PMC Article

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