The primary parameters, secondary and tertiary structures and transmembrane regions were compared in bioinformatics. Considerable differences were found among the four toxins compared each other in primary structure, and many similarities in secondary structure and transmembrane regions. The structural diversity is smallest in domain I, domain II is the most divergent domain, and Cry2Aa is the most divergent member. The surface potential over the four toxins were differently. Those structural diversity and similarity may be involved in determining action mode and insect specificity.

Key words: Bacillus thuringiensis, toxin, structure, bioinformatics, computer