IS AN AMPHIPHILIC REGION RESPONSIBLE FOR THE HEMOLYTIC-ACTIVITY OF BACILLUS-THURINGIENSIS TOXIN

The amino acid sequence of the 27 kDa protein responsible for the haem olytic activity of Bacillus thuringiensis subsp. israelensis toxin has been analysed by secondary structure prediction, helical wheel/net di agrams and molecular mechanics calculations. We found that segment 116 -126 presumably forms a strongly amphiphilic alpha-helix. This is supp orted by the findings that the synthesized segment 116-126 (a) has a s ignificant alpha-helical content in water, and (b) displays an in vitr o haemolytic activity comparable to that of bee venom peptide melittin . As segment 116-126 is present in the haemolyzing, but not present in the non-haemolyzing proteins from B. thuringiensis toxins, we suggest that this segment is responsible for the lytic potential of the B. th uringiensis subsp. israelensis protein. (C) Munksgaard 1993.