PHOSPHOLIPID SPECIES CONTAINING LONG AND VERY LONG POLYENOIC FATTY-ACIDS REMAIN WITH RHODOPSIN AFTER HEXANE EXTRACTION OF PHOTORECEPTOR-MEMBRANES
PHOSPHOLIPID SPECIES CONTAINING LONG AND VERY LONG POLYENOIC FATTY-ACIDS REMAIN WITH RHODOPSIN AFTER HEXANE EXTRACTION OF PHOTORECEPTOR-MEMBRANES
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DOI：
10.1021/bi00404a024
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发表时间：
1988-02-23
期刊：
影响因子：
2.9
通讯作者：
AVELDANO, MI
中科院分区：
文献类型：
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作者：
AVELDANO, MI
约四分之一的来自牛圆盘感光膜的磷脂酰胆碱（PC）含有n-3和n-6系列的极低链（24-36个碳）多不饱和（4、5和6个双键）脂肪酸（VLCPUFA）。这种脂肪酸，仅存在于二聚不饱和物质中，被酯化到其甘油主链的sn-1位，二十二碳六烯酸酯是sn-2位的主要脂肪酸。在色谱上，这种PC相对于其他物种显示出弱极性特征，这归因于它们的碳数量非常大。冻干磁盘的己烷提取后，PC是仍与视紫红质相关的脂质部分的主要成分，其次是磷脂酰丝氨酸，而大部分磷脂酰乙醇胺被去除。己烷可去除和蛋白质结合的脂质馏分的脂肪酸组成显着不同，后者富含含有长链和非常长链多烯的脂质物质。除游离脂肪酸外，所有脂质类别均观察到这一点。含有VLCPUFA的PC是视紫红质相关脂质组分中浓度最高的物质。这些PC在sn-1处具有的非常长的链多烯可以解释它们对与蛋白质分离的抗性。假设它们的异常长的多烯脂肪酸可以很好地适合于部分地围绕α-环己基脂肪酸。视紫红质的螺旋片段。
About one-fourth the phosphatidylcholines (PCs) from bovine disk photoreceptor membranes contain very low chain (24-36 carbons) polyunsaturated (4, 5, and 6 double bonds) fatty acids of the n-3 and n-6 series (VLCPUFA). Such fatty acids, exclusively occurring in dipolyunsaturated species, are esterified to the sn-1 position of their glycerol backbone, docosahexaenoate being the major fatty acid at sn-2. Chromatographically, such PCs display a weakly polar character relative to other species, ascribable to their exceedingly larger number of carbons. After hexane extraction of lyophilized disks, PC is the major component of the fraction of lipids that remains associated with rhodopsin, followed by phosphatidylserine, while a large proportion of the phosphatidylethanolamine is removed. The fatty acid composition of the hexane-removable and protein-bound lipid fractions markedly differs, the latter being enriched in lipid species containing long-chain and very long chain polyenes. This is observed for all lipid classes except for free fatty acids. VLCPUFA-containing PCs are the most highly concentrated species in the rhodopsin-associated lipid fraction. The very long chain polyenes these PCs have at sn-1 may account for their resistance to being separated from the protein. It is hypothesized that their unusually long polyenoic fatty acids could be well suited to partially surround .alpha.-helical segments of rhodopsin.