Effects of the terminal charges in human neutrophil alpha-defensin 2 on its bactericidal and membrane activity

Human neutrophil alpha-defensin 2 (HNP2) was N-terminally acetylated and/or C-terminally amidated, resulting in three terminally modified analogs, Ac-HNP2, HNP2-NH2 and Ac-HNP2-NH2. We examined their bactericidal activity against E. coli and S. aureus and their ability to induce leakage from large unilamellar vesicles. Loss of the N-terminal positive charge was functionally deleterious, whereas removal of the C-terminal negative charge enhanced microbial killing and membrane permeabilization. Our findings validate the importance of electrostatic forces in defensin-microbe interactions and point to the bacterial cytoplasmic membrane as a target of HNP2 activity.