Next Article in Journal
Mycotoxins in Ethiopia: A Review on Prevalence, Economic and Health Impacts
Previous Article in Journal
Ankle and Foot Spasticity Patterns in Chronic Stroke Survivors with Abnormal Gait
Previous Article in Special Issue
Characterization of Two Novel Bacillus thuringiensis Cry8 Toxins Reveal Differential Specificity of Protoxins or Activated Toxins against Chrysomeloidea Coleopteran Superfamily
Open AccessArticle

Rearrangement of N-Terminal α-Helices of Bacillus thuringiensis Cry1Ab Toxin Essential for Oligomer Assembly and Toxicity

Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos 62250, Mexico
*
Author to whom correspondence should be addressed.
Toxins 2020, 12(10), 647; https://doi.org/10.3390/toxins12100647
Received: 9 September 2020 / Revised: 28 September 2020 / Accepted: 28 September 2020 / Published: 8 October 2020
(This article belongs to the Special Issue The Pivotal Role of Toxins in Insects-Bacteria Interactions)
Cry proteins produced by Bacillus thuringiensis are pore-forming toxins that disrupt the membrane integrity of insect midgut cells. The structure of such pore is unknown, but it has been shown that domain I is responsible for oligomerization, membrane insertion and pore formation activity. Specifically, it was proposed that some N-terminal α-helices are lost, leading to conformational changes that trigger oligomerization. We designed a series of mutants to further analyze the molecular rearrangements at the N-terminal region of Cry1Ab toxin that lead to oligomer assembly. For this purpose, we introduced Cys residues at specific positions within α-helices of domain I for their specific labeling with extrinsic fluorophores to perform Föster resonance energy transfer analysis to fluorescent labeled Lys residues located in Domains II–III, or for disulfide bridges formation to restrict mobility of conformational changes. Our data support that helix α-1 of domain I is cleaved out and swings away from the toxin core upon binding with Manduca sexta brush border membrane vesicles. That movement of helix α-2b is also required for the conformational changes involved in oligomerization. These observations are consistent with a model proposing that helices α-2b and α-3 form an extended helix α-3 necessary for oligomer assembly of Cry toxins. View Full-Text
Keywords: Bacillus thuringiensis; Cry1ab toxin; oligomer assembly; Föster Resonance Energy Transfer (FRET); disulfide bridges Bacillus thuringiensis; Cry1ab toxin; oligomer assembly; Föster Resonance Energy Transfer (FRET); disulfide bridges
Show Figures

Graphical abstract

MDPI and ACS Style

Pacheco, S.; Quiliche, J.P.J.; Gómez, I.; Sánchez, J.; Soberón, M.; Bravo, A. Rearrangement of N-Terminal α-Helices of Bacillus thuringiensis Cry1Ab Toxin Essential for Oligomer Assembly and Toxicity. Toxins 2020, 12, 647.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop