Lipid–Protein Nanodiscs Offer New Perspectives for Structural and Functional Studies of Water-Soluble Membrane-Active Peptides

摘要

Lipid-protein nanodiscs (LPNs) are nanoscaled fragments of a lipid bilayer stabilized in solution by the apolipoprotein or a special membrane scaffold protein (MSP). In this work, the applicability of LPN-based membrane mimetics in the investigation of water-soluble membrane-active peptides was studied. It was shown that a pore-forming antimicrobial peptide arenicin-2 from marine lugworm (charge of +6) disintegrates LPNs containing both zwitterionic phosphatidylcholine (PC) and anionic phosphatidylglycerol (PG) lipids. In contrast, the spider toxin VSTx1 (charge of +3), a modifier of Kv channel gating, effectively binds to the LPNs containing anionic lipids (POPC/DOPG, 3 : 1) and does not cause their disruption. VSTx1 has a lower affinity to LPNs containing zwitterionic lipids (POPC), and it weakly interacts with the protein component of nanodiscs, MSP (charge of –6). The neurotoxin II (NTII, charge of +4) from cobra venom, an inhibitor of the nicotinic acetylcholine receptor, shows a comparatively low affinity to LPNs containing anionic lipids (POPC/DOPG, 3 : 1 or POPC/DOPS, 4 : 1), and it does not bind to LPNs/POPC. The obtained data show that NTII interacts with the LPN/POPC/DOPS surface inseveral orientations, and that the exchange process among complexes withdifferent topologies proceeds fast on the NMR timescale. Only one of thepossible NTII orientations allows for the previously proposed specificinteraction between the toxin and the polar head group of phosphatidylserinefrom the receptor environment (Lesovoy et al., Biophys. J. 2009. V. 97. №7. P. 2089–2097). These results indicate that LPNs can be used instructural and functional studies of water-soluble membrane-active peptides(probably except pore-forming ones) and in studies of the molecular mechanismsof peptide-membrane interaction.