title: tBid forms a pore in the liposome membrane.
abstract: We investigated the ability of tBid (truncated form of Bid) to bind and permeabilize the liposomes (large unilamellar vesicles, LUVs) and release fluorescent marker molecules (fluorescein-isothiocyanate-conjugated dextrans, FITC-dextrans) of various molecular diameters (FD-20, FD-70, FD-250S) from LUVs. Obtained data showed that tBid was more efficient in promoting leakage of FITC-dextrans from LUVs composed of cardiolipin and dioleoylphosphatidylcholine (DOPC) than LUVs made of dioleoylphosphatidic acid or dioleoylphosphatidylglycerol and DOPC. The leakage efficiency was reduced with increasing amount of dioleoylphosphatidylethanolamine or dielaidoylphosphatidylethanolamine. Phospholipid monolayer assay and fluorescence quenching measurements revealed that tBid inserted deeply into the hydrophobic acyl chain of acidic phospholipids. Taking into account the tBid three-dimensional structure, we propose that tBid could penetrate into the hydrophobic core of membrane, resulting in the leakage of entrapped content from LUVs via a pore-forming mechanism.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, PR China. yangfy@sun5.ibp.ac.cn
authors.forename: Ling
authors.initials: L
authors.lastname: Yan
authors.forename: Qi
authors.initials: Q
authors.lastname: Miao
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.forename: Fuyu
authors.initials: F
authors.lastname: Yang
mesh_terms: D000818:Animals; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003911:Dextrans / Q000737:chemistry / Q000493:pharmacokinetics; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry / Q000493:pharmacokinetics; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D010539:Permeability; D010712:Phosphatidic Acids / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000737:chemistry / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D011312:Pressure; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D002352:Carrier Proteins; D003911:Dextrans; D008081:Liposomes; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D011994:Recombinant Proteins; C037657:dioleoylphosphatidic acid; C051388:1,2-dioleoyl-sn-glycero-3-phosphoglycerol; C017251:1,2-oleoylphosphatidylcholine; D016650:Fluorescein-5-isothiocyanate