Clejan S, Bittman R, Rottem S
Biochemistry. 1981 Apr 14;20(8):2200-4. doi: 10.1021/bi00511a019.
Stopped-flow kinetic measurements of the association of filipin with sterols in intact cells and isolated membranes of Mycoplasma capricolum were used to study the effects of varying the phospholipid in the membrane. The phospholipid composition and content of the membrane were varied by growing cells in an albumin-containing medium with cholesterol, palmitic and oleic acids, and various concentrations of exogenous phospholipids. The exogenous phospholipids (phosphatidylcholine, sphingomyelin, and phosphatidic acid) were incorporated up to levels of approximately 50% of the total membrane phospholipids but had no effect on the distribution of cholesterol between the two halves of the membrane bilayer. The sterol structure was varied by growing the cells with 10/micrograms/mL of either cholesterol, beta-cholestanol, 4,6-cholestadien-3 beta-ol, ergosterol, beta-sitosterol, or stigmasterol. With cholesterol, beta-cholestanol, and 4,6-cholestadien-3 beta-ol, approximately 65% of the sterol was found to be present in the outer half of the lipid bilayer. With ergosterol, beta-sitosterol, and stigmasterol, about 89% of the sterol is localized in the outer half of the membrane bilayer. Thus, the behavior of the alkyl-substituted sterols differs from that of cholesterol. The extent to which a sterol is distributed asymmetrically between the two halves of the bilayer is not related to the extent to which maximum growth is produced. These results suggest that growth-supporting sterols need not be translocated extensively.
利用停流动力学测量法研究了菲律宾菌素与山羊支原体完整细胞及分离膜中固醇的结合情况，以探讨改变膜中磷脂对其的影响。通过在含有胆固醇、棕榈酸和油酸以及不同浓度外源磷脂的白蛋白培养基中培养细胞，改变膜的磷脂组成和含量。外源磷脂（磷脂酰胆碱、鞘磷脂和磷脂酸）的掺入量高达总膜磷脂的约50%，但对胆固醇在膜双层两半之间的分布没有影响。通过在含有10/微克/毫升胆固醇、β-胆甾烷醇、4,6-胆甾二烯-3β-醇、麦角固醇、β-谷甾醇或豆甾醇的培养基中培养细胞，改变固醇结构。对于胆固醇、β-胆甾烷醇和4,6-胆甾二烯-3β-醇，约65%的固醇存在于脂质双层的外半部分。对于麦角固醇、β-谷甾醇和豆甾醇，约89%的固醇位于膜双层的外半部分。因此，烷基取代固醇的行为与胆固醇不同。固醇在双层两半之间不对称分布的程度与产生最大生长的程度无关。这些结果表明，支持生长的固醇不需要大量转运。
