Orientation and Pore-Forming Mechanism of a Scorpion Pore-Forming Peptide Bound to Magnetically Oriented Lipid Bilayers

摘要

The orientation and pore-forming mechanisms of pandinin 2 (pin2), an antimicrobial peptide isolated from venom of the African scorpion Pandinus imperator, bound to magnetically oriented lipid bilayers were examined by ³¹P and ¹³C solid-state, and ¹⁵N liquid-state NMR spectroscopy. ³¹P NMR measurements at various temperatures, under neutral and acidic conditions, showed that membrane lysis occurred only under acidic conditions, and at temperatures below the liquid crystal-gel phase transition of the lipid bilayers, after incubation for two days in the magnet. Differential scanning calorimetry measurements showed that pin2 induced negative curvature strain in lipid bilayers. The ¹³C chemical shift values of synthetic pin2 labeled at Gly³, Gly⁸, Leu¹², Phe¹⁷, or Ser¹⁸ under static or slow magic-angle spinning conditions, indicate that pin2 penetrates the membrane with its average helical axis perpendicular to the membrane surface. Furthermore, amide H-D exchange experiments of ¹⁵N-Ala⁴, Gly⁸, and Ala⁹ triply-labeled pin2 suggest that this peptide forms oligomers and confirms that the N-terminal region creates membrane pores.