Membrane-surfactant interactions. The effect of Triton X-100 on sarcoplasmic reticulum vesicles.
The effect of Triton X-100 on purified sarcoplasmic reticulum vesicles has been studied by means of chemical, ultrastructural and enzymic techniques. At low detergent/membrane ratios (about 1 Triton X-100 per 60 phospholipid molecules) the only effect observed is an increase in vesicle permeability. Higher surfactant concentrations, up to a 1:1 detergent/phospholipid ratio, produce a large enhancement of ATPase activity. Membrane solubilization occurs as a critical phenomenon when the surfactant/phospholipid molar ratio reaches a value around 1.5:1, corresponding to 2 mumol Triton X-100/mg protein. At this point, the suspension turbidity drops, virtually all the protein and phospholipid is solubilized and every organized structure disappears. Simultaneously, a dramatic increase in the specific activity of the solubilized ATPase is observed. The sudden solubilization of almost all the bilayer components at a given detergent concentration is attributed to the relative simplicity of this membrane system. Solubilization takes place at the same surfactant/membrane ratio, at least between 0.5 and 4 mg membrane protein/ml. The non-solubilized residue seems to consist mainly of delipidized aggregated forms of ATPase.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002458:Cell Fractionation / Q000379:methods; D008563:Membrane Lipids / Q000032:analysis; D008565:Membrane Proteins / Q000032:analysis; D008854:Microscopy, Electron; D009132:Muscles / Q000201:enzymology / Q000648:ultrastructure; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure*; D012995:Solubility
D008563:Membrane Lipids; D008565:Membrane Proteins; D011092:Polyethylene Glycols; D017830:Octoxynol; D000252:Calcium-Transporting ATPases