PubMed · 4336209
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D Nathans, K J Danna. 1972-04-19. Specific origin in SV40 DNA replication.. https://doi.org/10.1038/newbio236200a0
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The integrity and the surface charge distribution of native low density lipoprotein (LDL) are prerequisites of its binding to the LDL receptor. Oxidation is one of the most important physiological effects resulting in an altered structure and metabolism of LDL. To reveal forces responsible for maintaining the intact structure of LDL in the absence of cells we have determined the kinetics of lipid peroxidation, changes in electrophoretic mobilities and size distributions of LDL samples as a function of Cu++ induced oxidative modification in a cell-free system at two different (50 mM and 150 mM) ionic strengths by electrophoretic and dynamic light scattering. Our data show that the lipid peroxidation is almost complete before LDL is degraded at 50 mM while a slight extent of lipid peroxidation is enough to result in the same effect at 150 mM. These suggest that both ionic and hydrophobic interactions are necessary to maintain the integrity of the LDL molecule.
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We have reconstituted the human placental transferrin receptor (hTfR) into phospholipid vesicles using either dialysis, dilution, or gel filtration. Several different detergents and phospholipids and a variety of lipid-to-protein weight ratios were tested. Preformed vesicles as well as detergent-solubilized phospholipids were used. Reconstituted mixtures were fractionated by sucrose density gradient centrifugation and screened for ferritransferrin binding activity, and peak fractions were analyzed by electron microscopy. The efficiency of reconstitution was strongly influenced by the choice of the phospholipids used and the reconstitution method. Best results were obtained when hTfR was dissolved with octylpolyoxyethylene, mixed with detergent-solubilized soy bean lecithin, and reconstituted by slow dialysis. The data show that hTfR capable of binding ferritransferrin was reconstituted into vesicles with an irregular surface and many protrusions. In addition the reconstitution of hTfR resulted in the formation of tubular structures proceeding from the vesicle surface, which may serve as an in vitro model for future studies on the relevance of self-assembly processes for cellular endocytosis.