Crystal (Cry) Proteins -

The cry gene of B. thuringiensis produces a protein, which forms crystalline inclusions in the bacterial spores. These crystal proteins are responsible for the insecticidal activities of this bacterium. The cry genes (or Cry proteins) have so far been grouped into 16 distinct groups, which either code for a 130 kD a or a 70 kD a protein.

These proteins are solubilized in the alkaline environment of insect midgut and are then prototypically processed to yield a 60 kD a toxic, core fragment (except in the case of cry IVD). The toxin function is localized in the N-terminal half of tile 130 kD a proteins; the C-terminal half of these proteins is highly conserved and is most likely involved in the crystal formation.