PS membrane asymmetry influences the folding and insertion of a transmembrane helix

摘要: The plasma membrane (PM) contains an asymmetric distribution of lipids between the inner and outer leaflets its bilayer. A lipid special interest in eukaryotic cells is negatively charged phosphatidylserine (PS). In healthy cells, PS actively sequestered to leaflet PM but can redistribute when cell damaged or at onset apoptosis. influence asymmetry loss on protein structure organization have not been widely addressed. Marginally hydrophobic proteins contain acidic residues their transmembrane sequence, which enable topological transitions after association. pH low insertion peptide (pHLIP), undergoes a reorientation inserts into pH, as name implies, useful well-characterized model for studying these transitions. Although it known that inclusion symmetric vesicles affects process pHLIP by lowering midpoint insertion, unclear how influences Here, we studied pHLIPs topology using freely-floating phosphatidylcholine (PC)/PS with enriched leaflet. We developed modified protocol create containing employed Annexin V labeled Alexa 568 fluorophore new probe quantifying asymmetry. For pHLIP, was affected surface charge difference bilayer caused leaflets. thus conclude consequences behavior membrane-associated proteins. corollary studies bilayers mimic may fail capture important aspects protein-membrane interactions.