Pardaxin permeabilizes vesicles more efficiently by pore formation than by disruption.
Pardaxin is a 33-amino-acid neurotoxin from the Red Sea Moses sole Pardachirus marmoratus, whose mode of action shows remarkable sensitivity to lipid chain length and charge, although the effect of pH is unclear. Here we combine optical spectroscopy and dye release experiments with laser scanning confocal microscopy and natural abundance (13)C solid-state nuclear magnetic resonance to provide a more complete picture of how pardaxin interacts with lipids. The kinetics and efficiency of release of entrapped calcein is highly sensitive to pH. In vesicles containing zwitterionic lipids (PC), release occurs most rapidly at low pH, whereas in vesicles containing 20% anionic lipid (PG), release occurs most rapidly at high pH. Pardaxin forms stable or transient pores in PC vesicles that allow release of contents without loss of vesicle integrity, whereas the inclusion of PG promotes total vesicle collapse. In agreement with this, solid-state nuclear magnetic resonance reveals that pardaxin takes up a trans-membrane orientation in 14-O-PC/6-O-PC bicelles, whereas the inclusion of 14-0-PG restricts it to contacts with lipid headgroups, promoting membrane lysis. Pore formation in zwitterionic vesicles is more efficient than lysis of anionic vesicles, suggesting that electrostatic interactions may trap pardaxin in several suboptimal interconverting conformations on the membrane surface.
Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
Brian S
BS
Vad
Kresten
K
Bertelsen
Charlotte Hau
CH
Johansen
Jan Mondrup
JM
Pedersen
Troels
T
Skrydstrup
Niels Chr
NC
Nielsen
Daniel E
DE
Otzen
D000595:Amino Acid Sequence; D005397:Fish Venoms / Q000737:chemistry / Q000378:metabolism*; D005452:Fluoresceins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010539:Permeability; D016062:Porosity; D011487:Protein Conformation; D011522:Protons; D053835:Unilamellar Liposomes / Q000737:chemistry* / Q000378:metabolism*
D005397:Fish Venoms; D005452:Fluoresceins; D008055:Lipids; D011522:Protons; D053835:Unilamellar Liposomes; C017603:pardaxin; C007740:fluorexon