Lateral Diffusion of Membrane Proteins: Consequences of Hydrophobic Mismatch and Lipid Composition
Lateral Diffusion of Membrane Proteins: Consequences of Hydrophobic Mismatch and Lipid Composition
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DOI：
10.1016/j.bpj.2010.06.036
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发表时间：
2010-09-08
影响因子：
3.4
通讯作者：
Poolman, Bert
中科院分区：
文献类型：
--
作者：
Ramadurai, Sivaramakrishnan;Duurkens, Ria;Poolman, Bert
生物膜是由大量的脂质物质组成的，这些脂质物质在疏水长度、饱和度、以及头基的电荷和大小方面不同。现在，我们提出的数据上的影响的烃链长度的脂质和头基组成的蛋白质在模型膜的横向流动性。三聚体谷氨酸转运蛋白（GItT）和单体乳糖转运蛋白（LacY）在巨大的单层囊泡中重建，这些囊泡由不同酰基链长度（14-22个碳原子）的不饱和磷酸胆碱脂质和不同比例的DOPE/DOPG/DOPC脂质组成。蛋白质和荧光脂质类似物的横向迁移率作为双层的疏水厚度（h）和脂质组合物的函数，使用荧光相关光谱法测定。LacY的扩散系数随着双层厚度的增加而减小，符合Saffman-Delbruck的连续流体动力学模型。对于GItT，迁移率在diC 18：1 PC处具有最大值，这接近于体内双层的疏水厚度。横向迁移率随DOPE浓度线性下降，但不受DOPG中阴离子脂质分数的影响。DOPG和DOPE的加入不影响GItT的活性。我们的结论是，双层的疏水厚度是膜中分子扩散的主要决定因素，但蛋白质的特定性质可能会导致偏离萨夫曼-德尔布鲁克模型。
Biological membranes are composed of a large number lipid species differing in hydrophobic length, degree of saturation, and charge and size of the headgroup. We now present data on the effect of hydrocarbon chain length of the lipids and headgroup composition on the lateral mobility of the proteins in model membranes. The trimeric glutamate transporter (GItT) and the monomeric lactose transporter (LacY) were reconstituted in giant unilamellar vesicles composed of unsaturated phosphocholine lipids of varying acyl chain length (14-22 carbon atoms) and various ratios of DOPE/DOPG/DOPC lipids. The lateral mobility of the proteins and of a fluorescent lipid analog was determined as a function of the hydrophobic thickness of the bilayer (h) and lipid composition, using fluorescence correlation spectroscopy. The diffusion coefficient of LacY decreased with increasing thickness of the bilayer, in accordance with the continuum hydrodynamic model of Saffman-Delbruck. For GItT, the mobility had its maximum at diC18:1 PC, which is close to the hydrophobic thickness of the bilayer in vivo. The lateral mobility decreased linearly with the concentration of DOPE but was not affected by the fraction of anionic lipids from DOPG. The addition of DOPG and DOPE did not affect the activity of GItT. We conclude that the hydrophobic thickness of the bilayer is a major determinant of molecule diffusion in membranes, but protein-specific properties may lead to deviations from the Saffman-Delbruck model.