title: Kinetics of lipid mixing between bicelles and nanolipoprotein particles.
abstract: Nanolipoprotein particles (NLPs), also known as nanodiscs, are lipid bilayers bounded by apolipoprotein. Lipids and membrane proteins cannot exchange between NLPs. However, the addition of bicelles opens NLPs and transfers their contents to bicelles, which freely exchange lipids and proteins. NLP-bicelle interactions may provide a new method for studying membrane protein oligomerization. The interaction mechanism was investigated by stopped flow fluorometry. NLPs with lipids having fluorescence resonance energy transfer (FRET) donors and acceptors were mixed with a 200-fold molar excess of dihexanoyl phosphatidylcholine (DHPC)/dimyristoyl phosphatidylcholine (DMPC) bicelles, and the rate of lipid transfer was monitored by the disappearance of FRET. Near or below the DMPC phase transition temperature, the kinetics were sigmoidal. Free DHPC and apolipoprotein were ruled out as participants in autocatalytic mechanisms. The NLP-bicelle mixing rate showed a strong temperature dependence (activation energy = 28 kcal/mol). Models are proposed for the NLP-bicelle mixing, including one involving fusion pores.
authors: Biology Department, University of Texas at San Antonio, San Antonio, TX 78249, USA.
authors: Ginny
authors: G
authors: Lai
authors: Biology Department, University of Puerto Rico, Ponce, PR, USA.
authors: Kevin Muñoz
authors: KM
authors: Forti
authors: Biology Department, University of Texas at San Antonio, San Antonio, TX 78249, USA; Biochemistry Department, University of Texas Health Science Center, San Antonio, TX 78229, USA. Electronic address: robert.renthal@utsa.edu.
authors: Robert
authors: R
authors: Renthal
mesh_terms: D001053:Apolipoproteins / Q000737:chemistry / Q000378:metabolism*; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008561:Membrane Fusion; D008823:Micelles; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001053:Apolipoproteins; D008051:Lipid Bilayers; D008823:Micelles; D010713:Phosphatidylcholines; C032166:1,2-hexanoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine
keywords: Bicelle; Fluorescence resonance energy transfer; Membrane fusion; Nanolipoprotein particle; Sigmoid kinetics; Stopped flow