Rawyler A, Siegenthaler P A
Laboratoire de Physiologie Végétale, Université de Neuchâtel, Switzerland.
Biochim Biophys Acta. 1996 Jan 12;1278(1):89-97. doi: 10.1016/0005-2736(95)00190-5.
Cyclodextrins (CDs) have been used in controlled lipid depletion of thylakoid membranes avoiding the use of either detergents or lipolytic enzymes. Spinach thylakoid membranes were first treated with different CDs under various conditions. After removal of the CDs by washing, the amounts of mono-- and digalactosyldiacylglycerol (MGDG and DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG), protein, pigment and plastoquinone remaining in the membranes were determined. The main results, obtained with alpha-CD and heptakis-(2,6-di-O-methyl)-beta-CD (DM-beta-CD), were as follows. (1)Acyl lipids were removed from thylakoid membranes by both CDs (DM-beta-CD being more efficient than alpha-CD; the extent of removal depended on both CD and chlorophyll concentrations. (2) alpha-CD presented a higher selectivity towards lip classes than did DM-beta-CD, but in both cases the removal order was SQDG > PG > MGDG > DGDG. (3) alpha-CD showed a preference for those lipids containing saturated 16-carbon acyl chains whereas DM-beta-CD was essentially insensitive to the fatty acid composition of the lipids. (4) The protein, chlorophyll and carotenoid contents of thylakoids were not affected by CD treatments. (5) Plastoquinones were removable but in small amounts only and with a low efficiency (DM-beta-CD > alpha-CD). (6) For all lipid classes, the extent of lipid removal was higher at 0 degrees than at 20 degrees C. (7) The presence of MgCl(2) reduced the removal of PG and SQDG but not affect galactolipid depletion levels. (8) Staple lipid depletion levels in thylakoid membranes were reached after 5-10 min of CD treatment at 0 degrees C. (9) Of the four CDs tested, only three (alpha-CD, beta-CD, and DM-beta-CD) promoted lipid depletion whereas one (hydroxypropyl-beta-CD) failed completely to do so. It is concluded that CD-mediated lipid removal provides a valuable and versatile tool to achieve controlled and specific lipid depletions in biological membranes. A few examples of the consequences of a CD-induced lipid depletion on fluorescence and electron transport properties of thylakoids are given to show the usefulness of CDs in the investigation of structure-function relationship in photosynthetic membranes.
环糊精（CDs）已被用于类囊体膜的可控脂质去除，避免使用洗涤剂或脂解酶。首先在各种条件下用不同的环糊精处理菠菜类囊体膜。通过洗涤去除环糊精后，测定膜中剩余的单半乳糖基二酰基甘油和双半乳糖基二酰基甘油（MGDG和DGDG）、磺基喹喔啉基二酰基甘油（SQDG）和磷脂酰甘油（PG）、蛋白质、色素和质体醌的含量。用α-环糊精和七（2,6-二-O-甲基）-β-环糊精（DM-β-CD）得到的主要结果如下：（1）两种环糊精都能从类囊体膜中去除酰基脂质（DM-β-CD比α-环糊精更有效；去除程度取决于环糊精和叶绿素的浓度）。（2）α-环糊精对脂质种类的选择性高于DM-β-CD，但在两种情况下，去除顺序都是SQDG＞PG＞MGDG＞DGDG。（3）α-环糊精对含有饱和16碳酰基链的脂质有偏好，而DM-β-CD对脂质的脂肪酸组成基本不敏感。（4）类囊体的蛋白质、叶绿素和类胡萝卜素含量不受环糊精处理的影响。（5）质体醌可以被去除，但量很少且效率低（DM-β-CD＞α-环糊精）。（6）对于所有脂质种类，脂质去除程度在0℃时高于20℃。（7）MgCl₂的存在降低了PG和SQDG的去除，但不影响半乳糖脂的去除水平。（8）在0℃下用环糊精处理5-10分钟后，类囊体膜中的主要脂质去除水平达到。（9）在测试的四种环糊精中，只有三种（α-环糊精、β-环糊精和DM-β-CD）促进脂质去除，而一种（羟丙基-β-环糊精）完全没有作用。结论是，环糊精介导的脂质去除为在生物膜中实现可控和特异性脂质去除提供了一种有价值且通用的工具。给出了一些环糊精诱导的脂质去除对类囊体荧光和电子传递特性影响的例子，以说明环糊精在光合膜结构-功能关系研究中的有用性。
