Improvement Of Solubilization Of Crystal Protein Cry7Ba1 From Bacillus Thuringiensis

Bacillus thuringiensis subsp.huazhongiensis YBT978 could produce a 130kDa- crystal protein Cry7Bal.Unlike some regular Insecticidal Crystal Proteins, the crystal protein of Bacillus thuringiensis subsp,huazhongiensis YBT978 could be dissolved only at pH values of≥12.5,and the regular Insecticidal Crystal Proteins could be dissolved in alkalescence buffer(pH9.5).It was proved that the crystal protein Cry7Bal could exhibits toxicity to Plutella xylostella only while it was not dissolved(LC₅₀:1.33μg/mL).CrylAc and CrylC are the representative crystal protein of Cryl produced rhombus crystal,and they could exhibits toxicity while it was dissolved in alkalescence buffer(pH9.5).In this study,the N-terminal and C-terminal of Cry7Bal were substituted by the N-terminal and C-terminal of CrylC and CrylAc. The 4 recombinants could not form the integrity crystals but only inclusion bodies. The results also indicated that,when the C-terminal of Cry7Ba1 was substituted,the recombinant crystal proteins(0184,0185)could be dissolved in alkalescence buffer (pH9.5) as Cry1Ac and Cry1C,and the toxicity has not be changed(LC₅₀:0184:1.32μg/mL;0185:1.39μg/mL);however,when the N-terminal fragment of Cry7Ba1 was substituted(0181,0183),it is still insoluble in alkalescence buffer(pH9.5).These data suggested that the property of insolubility of Cry7Ba1 was associated with the structure of C-terminal.This research could improve the solubility through swapping the C-terminal of Cry7Ba1,and supplied possibility for the crystal protein biocontrol application.