The involvement of two specific arginine residues in the action of HM-1 killer toxin was deduced from site-directed mutagenesis.

Abstract

Each of the four arginine residues in the HM-1 killer toxin was replaced by alanine using site-directed mutagenesis. The polymerase chain reaction (PCR)-constructed mutant gene was successfully expressed in HM-1 toxin resistant Saccharomyces cerevisiae. Among four HM-1 toxin analogues, R82A HM-1 toxin and R86A HM-1 toxin lost killer activity, while R61A HM-1 toxin and R85A HM-1 toxin retained activity. These results strongly indicate the importance of the arginine residues at positions 82 and 86 which are located in the C-terminal region of the HM-1 toxin for the action of killer activity.