Challenging the Chirality Paradigm in Peptide-Lipid Interactions

Abstract

Peptide-lipid interactions are assumed to be achiral, probably because it is often ignored that lipid membranes are chiral. Thus, native and mirror image forms of peptides that act by binding to lipid are expected to have identical biological activities. Cyclotides, membrane-active peptides expressed in plants with specificity for phosphatidylethanolamine (PE)-phospholipids,challenge this paradigm: kalata B1, the prototypic cyclotide, is more active than its mirror image. To investigate whether the membrane chirality explains differences between native kalata B1 and its enantiomer, we synthesised phospholipids with non-natural chirality. Using kalata B1 analogues, cell-based assays, NMR spectroscopy, fluorescence spectroscopy and surface plasmon resonance we demonstrated that mirror image forms of kalata B1 prefer to bind membranes of the same chirality and showed that kalata B1 recognises PE-headgroups in a chiral-independent manner, but inserts into phospholipid bilayers via a mechanism dependent on membrane chirality. This study shows that, contrary to the generally assumed, chiral environment of phospholipid membranes can modulate the activity of membrane-active peptides.