A comparison of protein crystal subunit sizes in Bacillus thuringiensis

We have employed gel electrophoresis to determine the number and size of the subunits present in the protein crystals from 16 strains of Baccillus thuringiensis. The calculated molecular weights (MW) fell into three major categories whose crystals exhibited the following protein banding patterns: type I, high MW only (140 000- 160 000); type II, both high MW and medium MW (60 000 and 150 000); and type III, low MW only (40 000 - 50 000). Interestingly, the type I and type II crystals were the expected bipyramidal diamonds whereas the type III crystals possessed a previously unreported tetrahedral shape.