Szolderits G, Hermetter A, Paltauf F, Daum G
Institut für Biochemie, Technische Universität Graz, Austria.
Biochim Biophys Acta. 1989 Nov 27;986(2):301-9. doi: 10.1016/0005-2736(89)90481-1.
A phospholipid transfer protein from yeast (Daum, G. and Paltauf, F. (1984) Biochim. Biophys. Acta 794, 385-391) was 2800-fold enriched by an improved procedure. The specificity of this transfer protein and the influence of membrane properties of acceptor vesicles (lipid composition, charge, fluidity) on the transfer activity were determined in vitro using pyrene-labeled phospholipids. The yeast transfer protein forms a complex with phosphatidylinositol or phosphatidylcholine, respectively, and transfers these two phospholipids between biological and/or artificial membranes. The transfer rate for phosphatidylinositol is 19-fold higher than for phosphatidylcholine as determined with 1:8 mixtures of phosphatidylinositol and phosphatidylcholine in donor and acceptor membrane vesicles. If acceptor membranes consist only of non-transferable phospholipids, e.g., phosphatidylethanolamine, a moderate but significant net transfer of phosphatidylcholine occurs. Phosphatidylcholine transfer is inhibited to a variable extent by negatively charged phospholipids and by fatty acids. Differences in the accessibility of the charged groups of lipids to the transfer protein might account for the different inhibitory effects, which occur in the order phosphatidylserine which is greater than phosphatidylglycerol which is greater than phosphatidylinositol which is greater than cardiolipin which is greater than phosphatidic acid which is greater than fatty acids. Although mitochondrial membranes contain high amounts of negatively charged phospholipids, they serve effectively as acceptor membranes, whereas transfer to vesicles prepared from total mitochondrial lipids is essentially zero. Ergosterol reduces the transfer rate, probably by decreasing membrane fluidity. This notion is supported by data obtained with dipalmitoyl phosphatidylcholine as acceptor vesicle component; in this case the transfer rate is significantly reduced below the phase transition temperature of the phospholipid.
通过一种改进的方法，来自酵母的磷脂转移蛋白（道姆，G.和帕尔陶夫，F.（1984年）《生物化学与生物物理学学报》794，385 - 391）得到了2800倍的富集。使用芘标记的磷脂在体外测定了这种转移蛋白的特异性以及受体囊泡的膜性质（脂质组成、电荷、流动性）对转移活性的影响。酵母转移蛋白分别与磷脂酰肌醇或磷脂酰胆碱形成复合物，并在生物膜和/或人工膜之间转移这两种磷脂。在供体和受体膜囊泡中磷脂酰肌醇与磷脂酰胆碱按1:8混合的情况下测定，磷脂酰肌醇的转移速率比磷脂酰胆碱高19倍。如果受体膜仅由不可转移的磷脂组成，例如磷脂酰乙醇胺，会发生适度但显著的磷脂酰胆碱净转移。磷脂酰胆碱的转移受到带负电荷的磷脂和脂肪酸不同程度的抑制。脂质带电基团对转移蛋白的可及性差异可能解释了不同的抑制作用，其发生顺序为磷脂酰丝氨酸大于磷脂酰甘油大于磷脂酰肌醇大于心磷脂大于磷脂酸大于脂肪酸。尽管线粒体膜含有大量带负电荷的磷脂，但它们有效地充当受体膜，而向由总线粒体脂质制备的囊泡的转移基本上为零。麦角固醇可能通过降低膜流动性来降低转移速率。用二棕榈酰磷脂酰胆碱作为受体囊泡成分获得的数据支持了这一观点；在这种情况下，转移速率在磷脂的相变温度以下显著降低。
