Elucidating the conformational behavior and membrane-destabilizing capability of the antimicrobial peptide ecPis-4s

Here we present studies of the structure and membrane interactions of ecPis-4 s, a new antimicrobial peptide from the piscidin family, which shows a wide-range of potential biotechnological applications. In order to understand the mode of action ecPis-4 s, the peptide was chemically synthesized and structural investigations in the presence of anionic POPC:POPG (3:1, mol:mol) membrane and SDS micelles were performed. CD spectroscopy demonstrated that ecPis-4 s has a high content of helical structure in both membrane mimetic media, which is in line with solution NMR spectroscopy that revealed an amphipathic helical conformation throughout the entire peptide chain. Solid-state NMR experiments of ecPis-4 s selectively labeled with ¹⁵N/²H and reconstituted into uniaxially oriented POPC:POPG membranes revealed an ideal partition of hydrophilic and hydrophobic residues within the bilayer interface. The peptide aligns in parallel to the membrane surface, a topology stabilized by aromatic side-chain interactions of the Phe-1, Phe-2 and Trp-9 with the phospholipids. ²H NMR experiments using deuterated lipids revealed that anionic lipid accumulates in the vicinity of the cationic peptide upon peptide-membrane binding.