title: 3D structure of the Yersinia entomophaga toxin complex and implications for insecticidal activity.
abstract: Toxin complex (Tc) proteins are a class of bacterial protein toxins that form large, multisubunit complexes. Comprising TcA, B, and C components, they are of great interest because many exhibit potent insecticidal activity. Here we report the structure of a novel Tc, Yen-Tc, isolated from the bacterium Yersinia entomophaga MH96, which differs from the majority of bacterially derived Tcs in that it exhibits oral activity toward a broad range of insect pests, including the diamondback moth (Plutella xylostella). We have determined the structure of the Yen-Tc using single particle electron microscopy and studied its mechanism of toxicity by comparative analyses of two variants of the complex exhibiting different toxicity profiles. We show that the A subunits form the basis of a fivefold symmetric assembly that differs substantially in structure and subunit arrangement from its most well characterized homologue, the Xenorhabdus nematophila toxin XptA1. Histopathological and quantitative dose response analyses identify the B and C subunits, which map to a single, surface-accessible region of the structure, as the sole determinants of toxicity. Finally, we show that the assembled Yen-Tc has endochitinase activity and attribute this to putative chitinase subunits that decorate the surface of the TcA scaffold, an observation that may explain the oral toxicity associated with the complex.
authors.affiliation: Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia. m.landsberg@imb.uq.edu.au
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Landsberg
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Jones
authors.forename: Rosalba
authors.initials: R
authors.lastname: Rothnagel
authors.forename: Jason N
authors.initials: JN
authors.lastname: Busby
authors.forename: Sean D G
authors.initials: SD
authors.lastname: Marshall
authors.forename: Robert M
authors.initials: RM
authors.lastname: Simpson
authors.forename: J Shaun
authors.initials: JS
authors.lastname: Lott
authors.forename: Ben
authors.initials: B
authors.lastname: Hankamer
authors.forename: Mark R H
authors.initials: MR
authors.lastname: Hurst
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D001427:Bacterial Toxins / Q000737:chemistry*; D002688:Chitinases / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D021621:Imaging, Three-Dimensional; D007306:Insecticides / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009036:Moths; D010572:Pest Control, Biological; D025941:Protein Interaction Mapping / Q000379:methods; D011506:Proteins / Q000737:chemistry; D013499:Surface Properties; D020593:Xenorhabdus / Q000378:metabolism; D015007:Yersinia / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D007306:Insecticides; D011506:Proteins; D002688:Chitinases