ID | 66578 |
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Author |
Takahashi, Hirokazu
Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University
Asakura, Mami
Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University
Ide, Toru
Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University
Hayakawa, Tohru
Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University
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Abstract | Cry4Aa, produced by Bacillus thuringiensis subsp. israelensis, exhibits specific toxicity to larvae of medically important mosquito genera. Cry4Aa functions as a pore-forming toxin, and a helical hairpin (α4-loop-α5) of domain I is believed to be the transmembrane domain that forms toxin pores. Pore formation is considered to be a central mode of Cry4Aa action, but the relationship between pore formation and toxicity is poorly understood. In the present study, we constructed Cry4Aa mutants in which each polar amino acid residues within the transmembrane α4 helix was replaced with glutamic acid. Bioassays using Culex pipiens mosquito larvae and subsequent ion permeability measurements using symmetric KCl solution revealed an apparent correlation between toxicity and toxin pore conductance for most of the Cry4Aa mutants. In contrast, the Cry4Aa mutant H178E was a clear exception, almost losing its toxicity but still exhibiting a moderately high conductivity of about 60% of the wild-type. Furthermore, the conductance of the pore formed by the N190E mutant (about 50% of the wild-type) was close to that of H178E, but the toxicity was significantly higher than that of H178E. Ion selectivity measurements using asymmetric KCl solution revealed a significant decrease in cation selectivity of toxin pores formed by H178E compared to N190E. Our data suggest that the toxicity of Cry4Aa is primarily pore related. The formation of toxin pores that are highly ion-permeable and also highly cation-selective may enhance the influx of cations and water into the target cell, thereby facilitating the eventual death of mosquito larvae.
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Note | The version of record of this article, first published in Current Microbiology, is available online at Publisher’s website: http://dx.doi.org/10.1007/s00284-023-03602-8
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Published Date | 2024-01-28
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Publication Title |
Current Microbiology
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Volume | volume81
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Issue | issue3
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Publisher | Springer Science and Business Media LLC
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Start Page | 80
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ISSN | 0343-8651
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NCID | AA00621783
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Content Type |
Journal Article
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language |
English
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OAI-PMH Set |
岡山大学
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Copyright Holders | © The Author(s) 2024
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File Version | publisher
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Related Url | isVersionOf https://doi.org/10.1007/s00284-023-03602-8
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License | http://creativecommons.org/licenses/by/4.0/
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Citation | Takahashi, H., Asakura, M., Ide, T. et al. Mutational analysis of the transmembrane α4-helix of Bacillus thuringiensis mosquito-larvicidal Cry4Aa toxin. Curr Microbiol 81, 80 (2024). https://doi.org/10.1007/s00284-023-03602-8
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Funder Name |
Okayama foundation for science and technology
Yakumo foundation for environmental science
Japan Society for the Promotion of Science
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助成番号 | 22K05676
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