AGBA. BIOGEN

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https://repositorio.udes.edu.co/handle/001/9403

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Examinando AGBA. BIOGEN por Autor "Alzate, Oscar"

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  • Publicación
    Acceso abierto
    Preferential Protection of Domains II and III of Bacillus thuringiensis Cry1Aa Toxin by Brush Border Membrane Vesicles
    (2010-12) Hussain, Syed-Rehan A.; Florez, Alvaro M.; Dean, Donald H.; Alzate, Oscar
    The surface exposed Leucine 371 on loop 2 of domain II, in Cry1Aa toxin, was mutated to Lysine to generate the trypsin-sensitive mutant, L371K. Upon trypsin digestion L371K is cleaved into approxima-tely 37 and 26 kDa fragments. These are separable on SDS-PAGE, but remain as a single molecule of 65 kDa upon purification by liquid chromatography. The larger fragment is domain I and a portion of domain II (amino acid residues 1 to 371). The smaller 26-kDa polypeptide is the remainder of domain II and domain III (amino acids 372 to 609). When the mutant toxin was treated with high dose of M. sexta gut juice both fragments were degraded. However, when incubated with M. sexta BBMV, the 26 kDa fragment (domains II and III) was preferentially protected from gut juice proteases. As previously reported, wild type Cry1Aa toxin was also protected against degradation by gut juice proteases when incubated with M. sexta BBMV. On the contrary, when mouse BBMV was added to the reaction mixture neither Cry1Aa nor L371K toxins showed resistance to M. sexta gut juice proteases and were degraded. Since the whole Cry1Aa toxin and most of the domain II and domain III of L371K are protected from proteases in the presence of BBMV of the target insect, we suggest that the insertion of the toxin into the membrane is complex and involves all three domains.
  • Publicación
    Acceso abierto
    Protein Engineering of Bacillus thuringiensis δ-Endotoxins
    (2012-03) Florez, Alvaro M.; Osorio, Cristina; Alzate, Oscar
    Protein engineering of insecticidal Bt δ-endotoxins is a powerful tool for designing novel Cry toxins with altered properties, including changing the toxin’s specificity. By following some elementary rules governing the structure/function relationship, it has been possible to create new toxins with modified properties including increased toxicity and binding affinity, enhanced ion-transport activity, and changes in insect specificity. These methods have also produced valuable information and have led to an improved understanding of the mode of action of these important biopesticides. The results discussed in this chapter derive from rational molecular design where protein structure is modified by incorporating single or multiple amino acid substitutions aimed at modifying specific protein functions. In this review, we analyze several protein modifications that have been successfully used for creating stable, functional proteins with minimal structural alterations. The understanding and proper use of protein engineering approaches may help in implementing appropriate pest management strategies by improving the efficacy of these toxins against insect pests.