Kinetics of fluorescent-labeled phosphatidylcholine transfer between nonspecific lipid transfer protein and phospholipid vesicles.
Recently, rat liver nonspecific lipid transfer protein (nsLTP) was shown to form a fluorescent complex when allowed to equilibrate with 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 N-(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 kinetics 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.
Nichols
J W
JW
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D004058:Diffusion; D007700:Kinetics; D008081:Liposomes; D008099:Liver / Q000378:metabolism*; D008433:Mathematics; D008962:Models, Theoretical; D010069:Oxadiazoles / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000138:chemical synthesis / Q000378:metabolism*; D051381:Rats
D002352:Carrier Proteins; D008081:Liposomes; D010069:Oxadiazoles; D010713:Phosphatidylcholines; C030363:lipid transfer protein; C053903:1-palmitoyl-2-(12-((7-nitro-2,1,3-benzoxadiazol-4-yl)amino)dodecanoyl)phosphatidylcholine; C017251:1,2-oleoylphosphatidylcholine; D009327:4-Chloro-7-nitrobenzofurazan