Structure analysis of the fourth transmembrane domain of Nramp1 in model membranes.
Structure analysis of the fourth transmembrane domain of Nramp1 in model membranes.
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DOI：
10.1016/j.bbamem.2008.02.005
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发表时间：
2008-06
期刊：
影响因子：
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通讯作者：
Rong Xue;Shuo Wang;Haiyan Qi;Yuande Song;Chunyu Wang;Fei Li
中科院分区：
文献类型：
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作者：
Rong Xue;Shuo Wang;Haiyan Qi;Yuande Song;Chunyu Wang;Fei Li
Nramp1（natural resistance-associated macrophage protein 1）是一种具有12个跨膜结构域的膜蛋白。作为一种质子偶联的二价金属阳离子转运蛋白，参与细胞内病原体的防御。Nramp1中发生在位于第四跨膜结构域（TM4）内的甘氨酸169处的致病突变表明该结构域的功能重要性。在本文中，我们研究了一个肽，对应于野生型Nramp1的TM4，在SDS胶束和2，2，2-三氟乙醇溶剂中，使用CD和NMR光谱的三维结构。我们已经发现，α-螺旋主要是在膜模拟环境中诱导的，并且C-末端残基的折叠受SDS胶束中的pH调节。该肽嵌入SDS胶束中并通过卷曲螺旋相互作用自缔合。在TFE中的肽的螺旋被延长向N-末端相比，在SDS胶束在酸性pH值和自缔合的肽也被观察到在TFE中。事实上，Mn 2+离子是可访问的Asp-14位于SDS胶束的内部被发现，并随着pH值的增加，结合亲和力增加。肽的自缔合可能提供了一个路径，Mn 2+离子通过膜。
Nramp1 (natural resistance-associated macrophage protein 1) is an integral membrane protein with 12 putative transmembrane domains. As a proton-coupled divalent metal cation transporter, it is involved in defense against intracellular pathogens. Disease-causing mutation in Nramp1 occurring at glycine 169 located within the fourth transmembrane domain (TM4) suggests functional importance of this domain. In this paper, we study the three-dimensional structures of a peptide, corresponding to the TM4 of the wild-type Nramp1, in SDS micelles and 2, 2, 2-trifluoroethanol solvent using CD and NMR spectroscopies. We have found that an α-helix is predominantly induced in membrane-mimetic environments and the folding of the C-terminal residues is regulated by the pH in the SDS micelles. The peptide is embedded in SDS micelles and self-associated by coiled-coil interactions. The helix of the peptide in TFE is lengthened towards the N-terminus compared with those in SDS micelles at acidic pH and the self-association of the peptide is also observed in TFE. The fact that Mn2+ions are accessible to Asp-14 located in the interior of SDS micelles is found and the binding affinity is increased with increasing pH. The self-association of the peptide may provide a path by which Mn2+ions pass through the membrane.