Serial femtosecond crystallography on in vivo-grown crystals drives elucidation of mosquitocidal Cyt1Aa bioactivation cascade

Bacillus thuringiensis israelensis (Bti) produces the naturally-crystalline proteinaceous toxin Cyt1Aa that is toxic to mosquito larvae. Here the authors grow recombinant nanocrystals of the Cyt1Aa protoxin in vivo and use serial femtosecond crystallography to determine its structure at different redox and pH conditions and by combining their structural data with further biochemical, toxicological and biophysical analyses provide mechanistic insights into the Cyt1Aa bioactivation cascade.