"Multi-Hit" Action Of Membrane Active Peptides: Towards Understanding Bacterial Cell Killing

Membrane active peptides represent a class of potent peptides that disrupt cell membranes, penetrate through them or form transmembrane pores via mechanisms that are not well understood. Understanding how these simple peptides induce such a large diversity of processes will provide insights into the function of antimicrobial peptides (AMPs) and related families such as fusion peptides. Here, we present a combined biophysical and molecular-dynamics study on the interaction of an AMP, BPC194:c(KKLKKFKKLQ), with model membranes and correlate to in vivo observations. Our results showed that the peptide partitions to the membranes, folds at the interface and subsequently penetrates deeper opening a stable pore (∼2 nm in diameter) characterized by MD, electrophysiology and confocal microscopy. Furthermore, FRET and cryo-EM experiments showed that the peptide is also able to cause membrane fusion. The observed growth inhibition and the rupturing of the E. coli outer and inner membrane at the onset of killing suggests that several processes take place at the cell envelope along with poration. On the basis of in vitro and in vivo data and MD simulations, we show for the first time how an AMP operates by “multi-hit” action.