Advances in 3-dimensional structure and function of insecticidal crystal proteins of Bacillus thuringiensis.

Three-dimensional structure of insecticidal crystal proteins of Bacillus thuringiensis has been revealed to be three distinct domains. It has been found that different Cry toxins share similar structures. Domain I, consisting of a bundle of alpha -helices in which a hydrophobic helix 5 is surrounded by 6 similar to7 amphipathic helices, plays a unique role in pore formation. Domain II, consisting of three antiparallel beta -sheets with a loop at each apex, is responsible for receptor binding. Domain III consists of two twisted, antiparallel beta -sheets forming alpha beta -sandwich with a "jelly roll" topology, it might prevent the activated toxin from excessive degradation.