1-2-dielaidoylphosphatidylethanolamine and phosphorylethanolamine

The effects of nonlamellar-prone lipids, diacylglycerol and phosphatidylethanolamine (PE), on the kinetic association of SecA with model membranes were examined by measuring changes in the intrinsic emission fluorescence with a stopped-flow apparatus. Upon interaction with standard liposomes composed of 50 mol% dioleolyphosphatidylcholine (DOPC) and 50 mol% of dioleoylphosphatidylglycerol (DOPG), the intrinsic fluorescence intensity of SecA was decreased after a lapse of time with a rate constant of 0.0049 s(-1). When the DOPC of the standard vesicles was gradually replaced with either dioeloyl PE (DOPE) or Escherichia coli (E. coli) PE, the rate constant increased appreciably as a function of PE concentration, in the order DOPE > E. coli PE. In addition, when the PE of E. coli PE/DOPG (50/50) vesicles was replaced with more than 5 mol% dioleoylglycerol (DOG), the rate constant further increased by 40%. The incorporation of nonlamellar-prone lipids in the vesicles also enhanced the binding of SecA to model membranes in the order DOPE > or = E. coli PE/DOG > E. coli PE > DOPC. These results provide the first kinetic evidence for the importance of nonlamellar-prone phospholipids for the association rate of SecA with membranes.

Topics: Adenosine Triphosphatases; Bacterial Proteins; Diglycerides; Escherichia coli Proteins; Ethanolamines; Flow Injection Analysis; Glycerophospholipids; Kinetics; Lipid Bilayers; Lipids; Liposomes; Membrane Transport Proteins; Membranes, Artificial; Models, Biological; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylglycerols; Protein Binding; SEC Translocation Channels; SecA Proteins; Spectrometry, Fluorescence