Structural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure

Sarah C. Lee, Svetla Stoilova-Mcphie, Laura Baxter, Vilmos Fülöp, Janey Henderson, Alison Rodger, David I. Roper, David J. Scott, Corinne J. Smith, J. Alun W Morgan

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

A recently identified class of proteins conferring insecticidal activity to several bacteria within the Enterobacteriaceae family have potential for control of commercially important insect pests. Here, we report the first purification, biophysical characterisation and 3-D structural analysis of one of the toxin components, XptA1, from Xenorhabdus nematophila PMFI296 to a resolution of 23 Å. Membrane binding studies indicate that the three-component toxin system has a different mode of action from that of proteins from Bacillus thuringiensis (Bt). Biophysical characterisation of XptA1 suggests a mechanism of action of XptA1 whereby it first binds to the cell membrane forming a structure with a central cavity and forms a complex with its partners XptB1 and XptC1 producing the full insecticidal toxin. The structure of XptA1 is shown by a combination of electron microscopy, ultracentrifugation and circular dichroism spectroscopy to be a 1.15 MDa tetramer with a cage-like structure. Each of the four symmetry-related subunits has three well-defined domains and a longitudinal twist with one end narrower than the other. One third of the residues of XptA1 are α-helical and it is suggested the subunits associate partly via an α-helical coiled-coil interaction. XptA1 itself shows the same secondary structure at neutral pH and in an alkaline environment up to pH10.5. This pH tolerance indicates that the folded XptA1 can pass through the midgut of Lepidopteran insects susceptible to the insecticidal toxin complex. This implies therefore that its folded structure is important for its biological activity.

Original languageEnglish (US)
Pages (from-to)1558-1568
Number of pages11
JournalJournal of Molecular Biology
Volume366
Issue number5
DOIs
StatePublished - Mar 9 2007
Externally publishedYes

Fingerprint

Insects
Xenorhabdus
Bacillus thuringiensis
Ultracentrifugation
Enterobacteriaceae
Circular Dichroism
Spectrum Analysis
Electron Microscopy
Proteins
Cell Membrane
Bacteria
Membranes

Keywords

  • Bacillus thuringiensis
  • cage-like structure
  • insecticidal toxin
  • tetramer
  • Xenorhabdus nematophila

ASJC Scopus subject areas

  • Virology

Cite this

Lee, S. C., Stoilova-Mcphie, S., Baxter, L., Fülöp, V., Henderson, J., Rodger, A., ... Morgan, J. A. W. (2007). Structural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure. Journal of Molecular Biology, 366(5), 1558-1568. https://doi.org/10.1016/j.jmb.2006.12.057

Structural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure. / Lee, Sarah C.; Stoilova-Mcphie, Svetla; Baxter, Laura; Fülöp, Vilmos; Henderson, Janey; Rodger, Alison; Roper, David I.; Scott, David J.; Smith, Corinne J.; Morgan, J. Alun W.

In: Journal of Molecular Biology, Vol. 366, No. 5, 09.03.2007, p. 1558-1568.

Research output: Contribution to journalArticle

Lee, SC, Stoilova-Mcphie, S, Baxter, L, Fülöp, V, Henderson, J, Rodger, A, Roper, DI, Scott, DJ, Smith, CJ & Morgan, JAW 2007, 'Structural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure', Journal of Molecular Biology, vol. 366, no. 5, pp. 1558-1568. https://doi.org/10.1016/j.jmb.2006.12.057
Lee, Sarah C. ; Stoilova-Mcphie, Svetla ; Baxter, Laura ; Fülöp, Vilmos ; Henderson, Janey ; Rodger, Alison ; Roper, David I. ; Scott, David J. ; Smith, Corinne J. ; Morgan, J. Alun W. / Structural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure. In: Journal of Molecular Biology. 2007 ; Vol. 366, No. 5. pp. 1558-1568.
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