Redesigning Bacillus thuringiensis Cry1Aa toxin into a mosquito toxin

The Bacillus thuringiensis crystal protein Cry1Aa is normally selectively active to caterpillar larvae. Through rational design, toxicity (microg/ml) to the mosquito Culex pipiens was introduced by selected deletions and substitutions of the loop residues of domain II. Toxicity to its natural target Manduca sexta was concomitantly abolished. The successful grafting of the alternate mosquito toxicity onto the original lepidopteran Cry1Aa toxin demonstrates the possibility of designing and engineering a desired toxicity into any toxin of a common scaffold by reshaping the receptor binding region with desired specificities.