Kinetics of cholesterol and phospholipid exchange between Mycoplasma gallisepticum cells and lipid vesicles. Alterations in membrane cholesterol and protein content.

摘要: Abstract The kinetics of exchange radiolabeled cholesterol and phospholipids between intact Mycoplasma gallisepticum cells unilamellar lipid vesicles were investigated over a wide range cholesterol/phospholipid molar ratio. change in ratio was achieved by adapting the sterol-requiring M. to grow cholesterol-poor media, providing with decreased unesterified content. At least 90% molecules unsealed membranes underwent at 37 degrees C as single kinetic pool presence albumin (2%, w/v). However, we observed biphasic cells, indicating that translocation from inner outer monolayers rate-limiting process. Approximately 50% localized each pool, independent vesicles. A striking parameters for occurred 20 26 mol % cholesterol; example, when 0.36 0.25, half-time equilibration two pools 4.6 +/- 0.5 2.5 0.1 h. Phospholipid rates also enhanced on decreasing membrane ability modulate its own rate, well phospholipids, is suggested arise sterol's regulate order. Extensive chemical modification surface cross-linking some protein constituents 1,4-phenylenedimaleimide rate. Depletion proteins treatment growing cultures chloramphenicol increased possibly because removal mass may impede translocation. observations phospholipid one order magnitude slower than dimethyl sulfoxide, potassium thiocyanate, salicylate rate are consistent mechanism involving diffusion through aqueous phase.