title: Cryptic endotoxic nature of Bacillus thuringiensis Cry1Ab insecticidal crystal protein.
abstract: Cry1Ab is one of the most studied insecticidal proteins produced by Bacillus thuringiensis during sporulation. Structurally, this protoxin has been divided in two domains: the N-terminal toxin core and the C-terminal portion. Although many studies have addressed the biochemical characteristics of the active toxin that corresponds to the N-terminal portion, there are just few reports studying the importance of the C-terminal part of the protoxin. Herein, we show that Cry1Ab protoxin has a unique natural cryptic endotoxic property that is evident when their halves are expressed individually. This toxic effect of the separate protoxin domains was found against its original host B. thuringiensis, as well as to two other bacteria, Escherichia coli and Agrobacterium tumefaciens. Interestingly, either the fusion of the C-terminal portion with the insecticidal domain-III or the whole N-terminal region reduced or neutralized such a toxic effect, while a non-Cry1A peptide such as maltose binding protein did not neutralize the toxic effect. Furthermore, the C-terminal domain, in addition to being essential for crystal formation and solubility, plays a crucial role in neutralizing the toxicity caused by a separate expression of the insecticidal domain much like a dot/anti-dot system.
authors.affiliation: Department of Surgery and the Vascular Biology Institute, University of Miami, R104, P.O. Box 019132, Miami, FL 33101, USA. rvazquez@med.miami.edu
authors.forename: Roberto I
authors.initials: RI
authors.lastname: Vazquez-Padron
authors.forename: Gustavo
authors.initials: G
authors.lastname: de la Riva
authors.forename: Guillermin
authors.initials: G
authors.lastname: Agüero
authors.forename: Yussun
authors.initials: Y
authors.lastname: Silva
authors.forename: Si M
authors.initials: SM
authors.lastname: Pham
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
authors.forename: Abdelouahab
authors.initials: A
authors.lastname: Aïtouche
mesh_terms: D016960:Agrobacterium tumefaciens / Q000378:metabolism; D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D015153:Blotting, Western; D002455:Cell Division; D002470:Cell Survival; D004731:Endotoxins / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006460:Hemolysin Proteins; D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D010455:Peptides; D011994:Recombinant Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis