Ovalbumin-induced fusion of acidic phospholipid vesicles at low pH.
The interactions of ovalbumin (OA) with large unilamellar vesicles (LUV) of phosphatidylserine (PS) and PS/phosphatidylethanolamine (PE) were studied. It was observed that OA induces aggregation, destabilization, and fusion of these LUV composed of acidic phospholipids at low pH levels. The fusion of LUV by OA was monitored by measuring the intermixing of internal aqueous contents of vesicles, by resonance energy transfer assay which follows the mixing of the membrane components, and by thin-sectioning electron microscopy. The pH profile of fusion was found to be similar to the pH-dependent binding of OA to the same phospholipid vesicles. Proteolytic digestion and hydrophobic labeling with dansyl chloride and photoreactive phosphatidylcholine (PC) of the OA-vesicle complex showed that a segment of OA with a molecular weight of approximately 2,500 penetrates the bilayer. The amino acid composition of this segment indicated that it is the 291-322 fragment and not the putative signal sequence.
Yun
C H
CH
Department of Biological Science and Engineering, Korea Advanced Institute of Science and Technology, Seoul.
Kim
H
H
D000596:Amino Acids / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008561:Membrane Fusion; D008563:Membrane Lipids / Q000032:analysis; D008854:Microscopy, Electron; D010047:Ovalbumin / Q000494:pharmacology*; D010743:Phospholipids / Q000032:analysis*; D010777:Photochemistry; D014357:Trypsin
D000596:Amino Acids; D008563:Membrane Lipids; D010743:Phospholipids; D010047:Ovalbumin; D014357:Trypsin