Activación de la Proteína Cry 11Bb de Bacillus Thuringiensis Subesp. Medellin Por Digestión Con Tripsina Y Extractos Intestinales de Larvas de Culex Quinquefasciatus (Diptera: Culicidae)

The ability of the larval midgut protease extracts from Culex quinquefasciatus and trypsin to process Bacillus thuringiensis subsp. medellin CryllBb toxin was investigated. The activity of midgut proteases increase with an increment in pH being the highest activity obtained at pH 10.6. A time course study showed partial fragmentation of the protein ultimately ending in the production of protease-resistant core fragments of relative molecular masses of 30 and 33 kDa. Proteases with trypsin specificity were detected in C. quinquefasciatus larval midgut extracts. This activity was detected by N-terminal amino acid sequence analysis of the Bacillus thuringiensis subsp. medellin Cry11Bb toxin proteolytic fragments. In vivo, the mosquito larvae processed the inclusions generating three fragments. The fragments fully retain their toxicity to C. quinquefasciatus first instar larvae. These data indicate the possible role of midgut proteases in B. thuringiensis subsp. medellin Cry11Bb toxin activation.