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固体NMR研究显示膜蛋白中不同结构域的运动性对水的依赖存在差异

(J. Phys. Chem. B, 2014, 118, 9553–9564)

   

  水对膜以及膜蛋白的结构、动力学和功能具有深远的影响。迄今为止,人们对膜蛋白分子运动的水依赖性知之甚少。为此,我们利用多维魔角旋转固体NMR研究了二酯酰甘油激酶(Diacylglycerol kinase, DAGK)/DMPC-DMPG体系的运动性,分别采用基于J-耦合或D-耦合的固体NMR实验分析了运动性强或运动性弱的结构域及其水接近性,揭示了DAGK中不同结构域的运动性对水的依赖性存在差异。结果显示:柔性残基(基于J-耦合观测)的快速、大幅度运动在样品含水量低于20%时不明显;当含水量在20-50%时,运动随着水含量增加而显著加快;当含水量在50%以上继续增加时,运动性没有进一步的增强。与此相反,当磷脂处于凝胶态时,刚性残基(基于D-耦合观测)的亚微秒运动与水含量无关;当磷脂处于凝胶-液晶态的转变点附近时,蛋白质分子在磷脂膜平面上的整体旋转与水含量密切相关——水增强了磷脂膜的流动性,从而促进分子的旋转运动。该研究为“水与膜蛋白动力学和功能的关联性”提供了新的例证。 

 

Solid-State NMR Shows That Dynamically Different Domains of Membrane Proteins Have Different Hydration Dependence 

Abstract     Hydration has a profound influence on the structure, dynamics, and functions of membrane and membrane-embedded proteins. So far the hydration response of molecular dynamics of membrane proteins in lipid bilayers is poorly understood. Here, we reveal different hydration dependence of the dynamics in dynamically different domains of membrane proteins by multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy using 121-residue integral diacylglycerol kinase (DAGK) in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DMPG) lipid bilayers as a model system. The highly mobile and immobile domains of DAGK and their water accessibilities are identified site-specifically by scalar- and dipolar-coupling based MAS ssNMR experiments, respectively. Our experiments reveal different hydration dependence of the dynamics in highly mobile and immobile domains of membrane proteins. We demonstrate that the fast, large-amplitude motions in highly mobile domains are not triggered until 20% hydration, enhanced at 20–50% hydration and unchanged at above 50% hydration. In contrast, motions on submicrosecond time scale of immobile residues are observed to be independent of the hydration levels in gel phase of lipids, and at the temperature near gel–liquid crystalline phase transition, amplitude of whole-molecule rotations around the bilayer normal is dominated by the fluidity of lipid bilayers, which is strongly hydration dependent. The hydration dependence of the dynamics of DAGK revealed by this study provides new insights into the correlations of hydration to dynamics and function of membrane proteins in lipid bilayers. 

 








 
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