Non-covalent cross-linking of lipid bilayers by myelin basic protein: a possible role in myelin formation.
Myelin basic protein associates with bilayer vesicles of pure egg phosphatidylcholine, L-alpha-dimyristoyl phosphatidylcholine and DL-alpha-dipalmitoyl phosphatidylcholine. Under optimum conditions the vesicles contain 15-18% of protein by weight. The binding to dipalmitoyl phosphatidylcholine is facilitated above its gel-to-liquid crystalline transition temperature. At low ionic strength the protein provokes a large increase in vesicle size and aggregation of these enlarged vesicles. Above a sodium chloride concentration of 0.07 M vesicle fusion is far less marked but aggregation persists. The pH- and ionic strength-dependence of this aggregation follows that of the protein alone; in both cases it occurs despite appreciable electrostatic repulsion between the associated species. A similar interaction was observed with diacyl phosphatidylserine vesicles. These observations, which contrast with earlier reports in the literature of a lack of binding of basic protein to phosphatidylcholine-containing lipids, demonstrate the ability of this protein to interact non-ionically with lipid bilayers. The strong cross-linking of lipid bilayers suggests a role for basic protein in myelin, raising the possibility that the protein is instrumental in collapsing the oligodendrocyte cell membrane and thus initiating myelin formation.
D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008081:Liposomes; D008854:Microscopy, Electron; D009185:Myelin Proteins / Q000096:biosynthesis*; D009994:Osmolar Concentration; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D011485:Protein Binding; D011663:Pulmonary Surfactants; D013053:Spectrophotometry
D008081:Liposomes; D009185:Myelin Proteins; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D011663:Pulmonary Surfactants