QUANTILATION OF THE PHASE PREFERENCES OF THE MAJOR LIPIDS OF THE ACHOLEPLASMA-LAIDLAWII B-MEMBRANE
QUANTILATION OF THE PHASE PREFERENCES OF THE MAJOR LIPIDS OF THE ACHOLEPLASMA-LAIDLAWII B-MEMBRANE
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DOI：
10.1021/bi00042a012
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发表时间：
1995-10-24
期刊：
影响因子：
2.9
通讯作者：
MCELHANEY, RN
中科院分区：
文献类型：
--
作者：
FOHT, PJ;TRAN, QM;MCELHANEY, RN
我们通过使用差示扫描量热法确定少量每种脂类对相同脂肪酸组成的磷脂酰乙醇胺基质的层状/反六方相变温度的影响，定量了脂肪酸均质磷脂酰乙醇胺膜的所有定量重要脂类的相偏好。我们发现，少量这些脂质的掺入产生的影响范围从适度降低到相应的磷脂酰乙醇胺的层状/反六方相变温度的显著升高。因此，尽管这种生物的总膜脂在生理条件下只形成片层相，但单个膜脂似乎表现出广泛的相偏好。磷脂酰甘油和二葡萄糖苷二酰基甘油似乎分别对层状液晶相有相对较强和较弱的偏好，而单葡萄糖苷，尤其是酰基聚戊烯基葡萄糖苷，则强烈倾向于反六方相。在这方面最值得注意的是，甘油磷酸基二葡糖基二酰基甘油的相偏好，它强烈地破坏了反六方相的稳定性，我们在随附的论文中表明[Lewis， R. N. A. H., & McElhaney， R. N.（1995）《生物化学》34,13818 -13824]实际上更倾向于分离的正常胶束相。在单个膜中存在正常的、层状的和反相的脂质，这对于理解脂质组织的物理基础和生物合成调控具有重要意义。研究还表明，单个膜脂对磷脂酰乙醇胺基质板层/反六方相转变温度的特征效应与其极性头基本征体积关系不明显。这一结果表明，这些脂类极性头基的有效横截面积一定受到电荷、水合作用、取向和运动自由度等因素以及内在头基体积的强烈影响。
We have quantitated the phase preferences of all of the quantitatively significant lipids of fatty acid-homogeneous Acholeplasma laidlawii membranes by determining the effect of small amounts of each lipid on the lamellar/reversed hexagonal phase transition temperature of a phosphatidylethanolamine matrix of identical fatty acid composition using differential scanning calorimetry. We find that the incorporation of small amounts of these lipids produce effects ranging from a moderate depression to a marked elevation of the lamellar/reversed hexagonal phase transition temperature of the corresponding phosphatidylethanolamine. Thus, although the total membrane lipids from this organism form only lamellar phases under physiological conditions, the individual membrane lipids appear to exhibit a wide range of phase preferences. Phosphatidylglycerol and diglucosyldiacylglycerol seem to have relatively strong and weak preferences for the lamellar liquid-crystalline phase, respectively, while monoglucosyldiacylglycerol, and especially acyl polyprenyl glucoside, strongly prefers the reversed hexagonal phase. Most notable in this regard is the phase preference of glycerylphosphoryldiglucosyldiacylglycerol, which strongly destabilizes the reversed hexagonal phase and which we show in the accompanying paper [Lewis, R. N. A. H., & McElhaney, R. N. (1995) Biochemistry 34, 13818-13824] actually prefers the normal micellar phase in isolation. The presence of normal, lamellar, and reversed phase-preferring lipids in a single membrane has important implications for understanding the physical basis of lipid organization and biosynthetic regulation in this and possibly in other organisms. We also show that the characteristic effect of the individual A. laidlawii membrane lipids on the lamellar/reversed hexagonal phase transition temperature of the phosphatidylethanolamine matrix is not well correlated with their polar headgroup intrinsic volumes. This result indicates that the effective cross-sectional area of the polar headgroups of these lipid species must be strongly influenced by factors such as charge, hydration, orientation, and motional freedom, as well as by intrinsic headgroup volume.