Publication: Potential prepore trimer formation by the Bacillus thuringiensis mosquito-specific toxin: Molecular insights into a critical prerequisite of membrane-bound monomers
Issued Date
2015-08-21
Resource Type
ISSN
1083351X
00219258
00219258
Other identifier(s)
2-s2.0-84939832278
Rights
Mahidol University
Rights Holder(s)
SCOPUS
Bibliographic Citation
Journal of Biological Chemistry. Vol.290, No.34 (2015), 20793-20803
Suggested Citation
Wilaiwan Sriwimol, Aratee Aroonkesorn, Somsri Sakdee, Chalermpol Kanchanawarin, Takayuki Uchihashi, Toshio Ando, Chanan Angsuthanasombat Potential prepore trimer formation by the Bacillus thuringiensis mosquito-specific toxin: Molecular insights into a critical prerequisite of membrane-bound monomers. Journal of Biological Chemistry. Vol.290, No.34 (2015), 20793-20803. doi:10.1074/jbc.M114.627554 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/35395
Research Projects
Organizational Units
Authors
Journal Issue
Thesis
Title
Potential prepore trimer formation by the Bacillus thuringiensis mosquito-specific toxin: Molecular insights into a critical prerequisite of membrane-bound monomers
Abstract
© 2015 by The American Society for Biochemistry and Molecular Biology, Inc. The insecticidal feature of the three-domain Cry δ-endotoxins from Bacillus thuringiensis is generally attributed to their capability to form oligomeric pores, causing lysis of target larval midgut cells. However, the molecular description of their oligomerization process has not been clearly defined. Here a stable prepore of the 65-kDa trypsin-activated Cry4Ba mosquito-specific toxin was established through membrane-mimetic environments by forming an ∼200-kDa octyl-β-D-glucoside micelle-induced trimer. The SDS-resistant trimer caused cytolysis to Sf9 insect cells expressing Aedes-mALP (a Cry4Ba receptor) and was more effective than a toxin monomer in membrane perturbation of calcein-loaded liposomes. A three-dimensional model of toxin trimer obtained by negative-stain EM in combination with single-particle reconstruction at ∼5 nm resolution showed a propeller-shaped structure with 3-fold symmetry. Fitting the three-dimensional reconstructed EM map with a 100-ns molecular dynamics-simulated Cry4Ba structure interacting with an octyl-β-D-glucoside micelle showed relative positioning of individual domains in the context of the trimeric complex with a major protrusion from the pore-forming domain. Moreover, high-speed atomic force microscopy imaging at nanometer resolution and a subsecond frame rate demonstrated conformational transitions from a propeller-like to a globularly shaped trimer upon lipid membrane interactions, implying prepore-to-pore conversion. Real-time trimeric arrangement of monomers associated with L-α-dimyristoylphosphatidyl-choline/3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonic acid bicelle membranes was also envisaged by successive high-speed atomic force microscopy imaging, depicting interactions among three individual subunits toward trimer formation. Together, our data provide the first pivotal insights into the structural requirement of membrane-induced conformational changes of Cry4Ba toxin monomers for the molecular assembly of a prepore trimer capable of inserting into target membranes to generate a lytic pore.