Domain I plays an important role in the crystallization of Cry3A in Bacillus thuringiensis |
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Authors: | Hyun-Woo Park Brian A Federici |
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Institution: | (1) Department of Entomology and Interdepartmental Graduate Programs in Genetics and Microbiology, University of California, Riverside, 92521 Riverside, CA |
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Abstract: | The insecticidal bacterium Bacillus thuringiensis synthesizes endotoxin Cry proteins of two size classes, 135 and 70 kDa, and both form crystalline inclusions in cells after
synthesis. Crystallization of 135-kDa proteins is due to intermolecular attraction of regions in the C-terminal half of the
molecule, and the N-terminal half fails to crystallize when synthesized in vivo. Alternatively, endotoxins of the 70-kDa class
such as Cry2A and Cry3A, which correspond to the N-terminal half of 135-kDa molecules, crystallize readily after synthesis.
Cry molecules of this size class consist of three principal domains, but the domains responsible for crystallization are not
known. To identify these domains, chimeric proteins were constructed in which Cry3A Domains I or III, or I and III were substituted
for the corresponding domains in truncated Cry1C molecules. Cry1C molecules with only Cry3A Domain III did not crystallize,
whereas when Cry3A Domains I and III, or Domain I alone, were substituted, large inclusions were obtained. Except for the
chimera consisting of Cry3A Domains I and III and Cry1C Domain II, most chimeras were not as stable as wild-type Cry3A or
truncated Cry1C. These results show that Cry3A Domain I plays an important role in its crystallization in vivo. |
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Keywords: | Bacillis thuringiensis protein crystallization insecticidal proteins domain structure domain function chimeric proteins |
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