Comprehensive Molecular Motion Capture for Sphingomyelin by Site-Specific Deuterium Labeling
Comprehensive Molecular Motion Capture for Sphingomyelin by Site-Specific Deuterium Labeling
复制标题
通过位点特异性氘标记对鞘磷脂进行全面的分子运动捕获
DOI：
10.1021/bi3009399
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发表时间：
2012
期刊：
影响因子：
2.9
通讯作者：
Nobuaki Matsumori
中科院分区：
文献类型：
--
作者：
山下琢矢; 鎌田春彦 他;Nobuaki Matsumori
脂筏因其在膜相关过程中的重要功能而备受关注。神经鞘蛋白和胆固醇被认为是形成脂筏所必需的，然而，尽管有大量的研究，但对它们的运动特性还没有完全了解。在这里，我们展示了围绕整个鞘磷脂分子的准确局部运动，这些运动是通过测量19种位置特异的鞘磷脂的四极分裂来捕获的(即，鞘磷脂的分子运动捕获)。四极分裂谱不同于报道的来自全氚神经鞘磷脂或模拟研究的分裂谱，表明胆固醇能更有效地促进烷基链中部的有序性，而不是浅层。与二肉豆蔻酰磷胆碱双层膜的比较表明，鞘磷脂双层膜中的胆固醇更深，这可能解释了所谓的伞状效应。实验还表明：(I)C2‘-C3’键主要采取Guche构象，(Ii)胆固醇在鞘磷脂双层中的净有序性不大于在磷脂酰胆碱双层中的净有序效应，(Iii)胆固醇对酰基或鞘氨醇没有特定的偏好，(Iv)酰基和鞘氨醇链似乎错配了大约两个亚甲基长度，以及(V)鞘磷脂链上部区域的运动与下部区域的运动对温度的依赖性较小，这可能是由于SM分子之间形成了分子间氢键。这些对鞘磷脂原子水平动力学的洞察为理解RAFT的形成机制提供了关键线索。
Lipid rafts have attracted much attention because of their significant functional roles in membrane-associated processes. It is thought that sphingomyelin and cholesterol are essential for forming lipid rafts; however, their motion characteristics are not fully understood despite numerous studies. Here we show accurate local motions encompassing an entire sphingomyelin molecule, which were captured by measuring quadrupole splittings for 19 kinds of site-specifically deuterated sphingomyelins (that is,molecular motion captureof sphingomyelin). The quadrupole splitting profiles, which are distinct from those reported from perdeuterated sphingomyelins or simulation studies, reveal that cholesterol enhances the order in the middle parts of the alkyl chains more efficaciously than at the shallow positions. Comparison with dimyristoylphosphocholine bilayers suggests that cholesterol is deeper in sphingomyelin bilayers, which likely explains the so-called umbrella effect. The experiments also demonstrate that (i) the C2′–C3′ bond predominantly takes the gauche conformation, (ii) the net ordering effect of cholesterol in sphingomyelin bilayers is not larger than that in phosphatidylcholine bilayers, (iii) cholesterol has no specific preference for the acyl or sphingosine chain, (iv) the acyl and sphingosine chains seem mismatched by about two methylene lengths, and (v) the motion of the upper regions of sphingomyelin chains is less temperature dependent than that of lower regions probably due to intermolecular hydrogen bond formation among SM molecules. These insights into the atomic-level dynamics of sphingomyelin provide critical clues to understanding the mechanism of raft formation.