Reconstruction of Bacillus thuringiensis ssp. israelensis Cry11A Endotoxin from Fragments Corresponding to Its N- and C-Moieties Restores Its Original Biological Activity

L. P. Revina¹, L. I. Kostina¹, L. A. Ganushkina², A. L. Mikhailova¹, I. A. Zalunin^1*, and G. G. Chestukhina¹

¹Scientific Research Institute for Genetics and Selection of Industrial Microorganisms, I Dorozhny Proezd 1, Moscow 117545, Russia; fax: (7-095) 315-0501; E-mail: zalunin@genetika.ru

²Marcinovsky Institute of Medical Parasitology and Tropical Medicine, Sechenov Moscow Medical Academy, Bolshaya Pirogovskaya ul. 2, Bldg. 3, Moscow 119992, Russia

^* To whom correspondence should be addressed.

Received January 28, 2003; Revision received March 25, 2003

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Subtilisin hydrolyzes Cry11A endotoxin (of 70 kD) produced by Bacillus thuringiensis ssp. israelensis to fragments of 33- and 36-kD, which correspond to N- and C-terminal halves of the endotoxin molecule. Thermitase (a serine protease from Thermoactinomyces vulgaris) and insect gut proteases from Diptera and Lepidoptera exhibit the same hydrolytic effect on Cry11A. Hydrolyzates maintain high toxicity with respect to larvae of Aedes aegypti, Anopheles stephensi, and Culex pipiens. The 33- and 36-kD Cry11A endotoxin components purified by ion-exchange chromatography from the subtilisin hydrolyzate were inactive; however, equimolar mixture of these proteins exhibited almost the same activity as the initial hydrolyzate.

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KEY WORDS: Cry11A endotoxin, Bacillus thuringiensis ssp. israelensis, limited proteolysis, mosquitocidal activity

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