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An α-amylase is a novel receptor for Bacillus thuringiensis ssp. israelensis Cry4Ba and Cry11Aa toxins in the malaria vector mosquito Anopheles albimanus (Diptera: Culicidae)

Authors

  • Maria Teresa Fernandez-Luna,

    1. Depto. de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Apdo. Postal 510-3, Cuernavaca, Morelos 62250, México.
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  • Humberto Lanz-Mendoza,

    1. Centro de Investigación sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, Morelos 62508, México.
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  • Sarjeet S. Gill,

    1. Department of Cell Biology and Neuroscience, University of California, Riverside, CA 92521, USA.
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  • Alejandra Bravo,

    1. Depto. de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Apdo. Postal 510-3, Cuernavaca, Morelos 62250, México.
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  • Mario Soberon,

    1. Depto. de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Apdo. Postal 510-3, Cuernavaca, Morelos 62250, México.
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  • Juan Miranda-Rios

    Corresponding author
    1. Depto. de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Apdo. Postal 510-3, Cuernavaca, Morelos 62250, México.
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    • Present address: Unidad de Genética de la Nutrición, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, and Instituto Nacional de Pediatría, México DF, 04510, México.


*E-mail riosjuanm@biomedicas.unam.mx; Tel. (+52) 5556226423; Fax (+52) 5556063489.

Summary

Bacillus thuringiensis ssp. israelensis (Bti) produces four Cry toxins (Cry4Aa, Cry4Ba, Cry10Aa and Cry11Aa), and two Cyt proteins (Cyt1Aa and Cyt2Ba), toxic to mosquito-larvae of the genus Aedes, Anopheles and Culex, important human disease vectors that transmit dengue virus, malaria and filarial parasites respectively. Previous work showed that Bti is highly toxic to Anopheles albimanus, the main vector for transmission of malaria in Mexico. In this work, we analysed the toxicity of isolated Cry proteins of Bti and identified an An. albimanus midgut protein as a putative Cry4Ba and Cry11Aa receptor molecule. Biossays showed that Cry4Ba and Cry11Aa of Bti are toxic to An. albimanus larvae. Ligand blot assays indicated that a 70 kDa glycosylphosphatidylinositol-anchored protein present in midgut brush border membrane vesicles of An. albimanus interacts with Cry4Ba and Cry11Aa toxins. This protein was identified as an α-amylase by mass spectrometry and enzymatic activity assays. The cDNA that codes for the α-amylase was cloned by means of 5′- and 3′-RACE experiments. Recombinant α-amylase expressed in Escherichia coli specifically binds Cry4Ba and Cry11Aa toxins.

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