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The elimination of DNA from the Cry toxin-DNA complex is a necessary step in the mode of action of the Cry8 toxin.

Ai B, Li J, Feng D, Li F, Guo S - PLoS ONE (2013)

Bottom Line: However, the role of the DNA associated with the activated toxin in the mechanism of action of the Cry toxin has long been ignored.In contrast, the association of DNA with each toxin might result in the nonspecific recognition of the Cry toxin and its target receptor in the insect midgut.Based on our results, we propose an additional step in the mechanism of action of the Cry8 toxin and elucidate the function of the associated DNA as well as the importance of the removal of this DNA for the insecticidal activity of the toxin.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science, Beijing Institute of Technology, Beijing, China.

ABSTRACT
Several crystal (Cry) proteins are known to occur as DNA-protein complexes. However, the role of the DNA associated with the activated toxin in the mechanism of action of the Cry toxin has long been ignored. Here, we focused on the DNA-activated Cry toxin complex. Both forms of the Cry8Ca2 and Cry8Ea1 toxins, i.e., with or without bound DNA, were separately obtained. Size-exclusion chromatography analysis indicated that the Cry8Ca2 toxin-DNA complex has a tight or compact structure. The Cry8Ca2 toxin-DNA complex is more likely to move toward the air/water interface and is more hydrophobic than the toxin without DNA. Competitive binding assays indicated that the Cry8Ca2 and Cry8Ea1 toxins without DNA specifically bind to the midgut of Anomala corpulenta and Holotrichia parallela larvae, respectively. In contrast, the association of DNA with each toxin might result in the nonspecific recognition of the Cry toxin and its target receptor in the insect midgut. The association of the DNA fragment with the Cry8 toxin was shown to protect the Cry protein from digestion by proteases. Based on our results, we propose an additional step in the mechanism of action of the Cry8 toxin and elucidate the function of the associated DNA as well as the importance of the removal of this DNA for the insecticidal activity of the toxin.

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The mechanism of action of the Cry toxin including the proposed role of the toxin-bound DNA.
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pone-0081335-g008: The mechanism of action of the Cry toxin including the proposed role of the toxin-bound DNA.

Mentions: In conclusion, we propose a supplemental step in the mode of action of the Cry8 toxin (Fig. 8), which emphasizes the presence of DNA associated with the activated toxin and requires the elimination of the DNA for the insecticidal activity of the toxin. Accordingly, variations in the DNase activity in insects may also result in tolerance to the Cry toxin, which requires further investigation. The presence and role of DNA in other Cry toxins should be further analyzed.


The elimination of DNA from the Cry toxin-DNA complex is a necessary step in the mode of action of the Cry8 toxin.

Ai B, Li J, Feng D, Li F, Guo S - PLoS ONE (2013)

The mechanism of action of the Cry toxin including the proposed role of the toxin-bound DNA.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852532&req=5

pone-0081335-g008: The mechanism of action of the Cry toxin including the proposed role of the toxin-bound DNA.
Mentions: In conclusion, we propose a supplemental step in the mode of action of the Cry8 toxin (Fig. 8), which emphasizes the presence of DNA associated with the activated toxin and requires the elimination of the DNA for the insecticidal activity of the toxin. Accordingly, variations in the DNase activity in insects may also result in tolerance to the Cry toxin, which requires further investigation. The presence and role of DNA in other Cry toxins should be further analyzed.

Bottom Line: However, the role of the DNA associated with the activated toxin in the mechanism of action of the Cry toxin has long been ignored.In contrast, the association of DNA with each toxin might result in the nonspecific recognition of the Cry toxin and its target receptor in the insect midgut.Based on our results, we propose an additional step in the mechanism of action of the Cry8 toxin and elucidate the function of the associated DNA as well as the importance of the removal of this DNA for the insecticidal activity of the toxin.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science, Beijing Institute of Technology, Beijing, China.

ABSTRACT
Several crystal (Cry) proteins are known to occur as DNA-protein complexes. However, the role of the DNA associated with the activated toxin in the mechanism of action of the Cry toxin has long been ignored. Here, we focused on the DNA-activated Cry toxin complex. Both forms of the Cry8Ca2 and Cry8Ea1 toxins, i.e., with or without bound DNA, were separately obtained. Size-exclusion chromatography analysis indicated that the Cry8Ca2 toxin-DNA complex has a tight or compact structure. The Cry8Ca2 toxin-DNA complex is more likely to move toward the air/water interface and is more hydrophobic than the toxin without DNA. Competitive binding assays indicated that the Cry8Ca2 and Cry8Ea1 toxins without DNA specifically bind to the midgut of Anomala corpulenta and Holotrichia parallela larvae, respectively. In contrast, the association of DNA with each toxin might result in the nonspecific recognition of the Cry toxin and its target receptor in the insect midgut. The association of the DNA fragment with the Cry8 toxin was shown to protect the Cry protein from digestion by proteases. Based on our results, we propose an additional step in the mechanism of action of the Cry8 toxin and elucidate the function of the associated DNA as well as the importance of the removal of this DNA for the insecticidal activity of the toxin.

Show MeSH