Kinetics of fluorescent-labeled phosphatidylcholine transfer between nonspecific lipid transfer protein and phospholipid vesicles.
Kinetics of fluorescent-labeled phosphatidylcholine transfer between nonspecific lipid transfer protein and phospholipid vesicles.
复制标题
非特异性脂质转移蛋白和磷脂囊泡之间荧光标记的磷脂酰胆碱转移的动力学。
DOI：
10.1021/bi00406a014
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Nichols,JW
中科院分区：
文献类型：
--
作者：
Nichols,JW
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322 Received September 3, 1987; Revised Manuscript Received November 18, 1987 abstract: Recently, rat liver nonspecific lipid transfer protein (nsLTP) was shown to form a fluorescent complex when allowed to equilibratewith self-quenching vesicles prepared from the fluorescent phospholipid 1-palmitoyl-2-[12-[(7-nitro-2, 1, 3-benzoxadiazol-4-yl) amino] dodecanoyl] phosphatidylcholine (P-C12-NBD-PC)[Nichols, J. W.(1987) J. Biol. Chem. 262, 14172-14177], Investigation of the mechanism of complex formation was continued by studying the kinetics of transfer of P-C12-NBD-PC between nsLTP and phospholipid vesicles using a transfer assay based on resonance energy transfer between P-C12-NBD-PC and A-(lissamine rhodamine B sulfonyl) dioleoylphosphatidylethanolamine. The principles of mass action kinetics (which predict initial lipid transfer rates as a function of protein and vesicle concentration) were used to derive equations for two distinct mechanisms: lipid transfer by the diffusion of monomers through the aqueous phase and lipid transfer during nsLTP-membrane collisions. The results of these kinetic studies indicated that the model for neither mechanism alone adequately predicted the initial rates of formation and dissolution of the P-C12-NBD-PC-nsLTP complex. The initial rate kinetics for both processes were predicted best by a model in which monomer diffusion and collision-dependent transfer occur simultaneously. These data support the hypothesis that the phospholipid-nsLTP complex functions as an intermediate in the transfer of phospholipids between membranes.^ Nonspecific lipid transfer protein (nsLTP) 1 stimulates the transfer of a wide range of lipids between membranes (Bloj & Zilversmit, 1977, 1981). Recently, nsLTP was shown to form a water-soluble phospholipid-nsLTP complex when allowed to equilibrate with bilayer vesicles prepared from fluorescent-labeled phospholipid, P-C12-NBD-PC (Nichols, 1987a). Prior to this observation, attempts to demonstrate a phospholipid-nsLTP complexusing radiolabeled phospholipids and traditional separation techniques failed (Crain& Zil-versmit, 1980; Van Amerongen et al., 1985), and as a result, nsLTP was proposed to function by mechanisms not involving the direct binding of phospholipids. For example, nsLTP has been proposed to function by the formation of a ternary complex between nsLTP and the donor and acceptor mem-branes which would facilitate the rapid intermembrane transfer of lipids (VanAmerongen et al., 1985; Altamura & Landriscina, 1986; Megli et al., 1986). Alternatively, nsLTP has been proposed to bind to membranes and increase the rate of lipid dissociation into the waterphase (Thompson, 1982; Nichols & Pagano, 1983). The demonstration that nsLTP binds phospholipids suggests that the resulting phospholipidnsLTP complex may mediate the intermembrane transfer. The observation that the thiol reagent mersalyl blocks both nsLTP binding of phospholipids (Nichols, 1987a) and its ability to stimulate intermembrane phospholipid transfer (Van Amer-
