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Title

Proteolytic processing of native Cry1Ab toxin by midgut extracts and purified trypsins from the Mediterranean corn borer Sesamia nonagrioides

AuthorsDíaz-Mendoza, Mercedes CSIC ORCID; Farinós, Gema P. CSIC ORCID ; Castañera, Pedro CSIC; Hernández-Crespo, Pedro CSIC ORCID ; Ortego, Félix CSIC ORCID
KeywordsBt-toxin
lepidoptera
digestive physiology
Bt maize
resistance
Issue DateMay-2007
PublisherElsevier
CitationJournal of Insect Physiology 53(5):428-435(2007)
AbstractThe proteolytic processing of native Cry1Ab toxin by midgut extracts from the Mediterranean corn borer, Sesamia nonagrioides, takes place in successive steps. Several cuts occur until a 74 kDa protein is obtained; this is further digested to give rise to an active form of 69 kDa, which can be again processed to fragments of 67, 66 and 43 kDa. We have shown that three different trypsins (TI, TIIA and TIII) purified from the S. nonagrioides midgut were able to digest Cry1Ab protoxin to obtain the active form of 69 kDa. Interestingly, TI and TIII further hydrolyzed the 69 kDa protein to a fragment of slightly lower molecular mass (67 kDa), while TIIA was able to continue digestion to give fragments of 46 and 43 kDa. These results contrast with those obtained using bovine trypsin, in which the main product of Cry1Ab digestion is a 69 kDa protein. The digestion of the toxin with a “non-trypsin” fraction from S. nonagrioides midgut lumen, mostly containing chymotrypsins and elastases and free of trypsin-like activity, resulted in a different processing pattern, yielding fragments of 79, 77, 71, 69 and 51 kDa. Our results indicate that trypsins and other proteases are involved in the first steps of protoxin processing, but trypsins play the most important role in obtaining the 74 and 69 kDa proteins. All the digestion products, including the proteins of 46 and 43 kDa obtained from the digestion of Cry1Ab by TIIA, were toxic to neonate larvae, indicating that none of the tested proteases contribute to toxin degradation in a significant manner
Description8 páginas, 3 figuras -- PAGS nros. 428-435
Publisher version (URL)http://dx.doi.org/10.1016/j.jinsphys.2006.12.015
URIhttp://hdl.handle.net/10261/61925
DOI10.1016/j.jinsphys.2006.12.015
ISSN0022-1910
E-ISSN1879-1611
Appears in Collections:(CIB) Artículos




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