FIG. 5.

Helical wheel of 18 residues in helix α4, including the 10 mutagenized residues (E129 to N138). Mutations which resulted in the loss of toxicity (including one double mutant) are indicated by solid arrows. Changes with no resultant loss of toxicity are indicated by dashed arrows. The asterisk indicates an increase in toxicity. Parentheses indicate double mutations. The hydrophobic and hydrophilic faces are demarcated by the internal lines.