Sub-nanometre mapping of the aquaporin-water interface using multifrequency atomic force microscopy.
Sub-nanometre mapping of the aquaporin-water interface using multifrequency atomic force microscopy.
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DOI：
10.1039/c6sm00751a
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发表时间：
2017-01
期刊：
影响因子：
3.4
通讯作者：
M. Ricci;R. Quinlan;Kislon Voïtchovsky
中科院分区：
文献类型：
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作者：
M. Ricci;R. Quinlan;Kislon Voïtchovsky
水通道蛋白是一种完整的膜蛋白，它调节水和小分子的进出细胞的运输。在眼晶状体组织中，水、离子和代谢物的循环是由微循环系统保证的，其中水通道蛋白-0(AQP0)起着核心作用。AQP0允许水通过晶状体膜，超出扩散限制。AQP0自然排列在正方形晶格中。AQP0的功能障碍与白内障等多种疾病有关。尽管对其结构、功能和动力学进行了大量的研究，但蛋白质与周围液体之间的界面以及晶格排列对膜界面水行为的影响仍不完全清楚。在这里，我们使用多频原子力显微镜(AFM)方法，以亚纳米分辨率绘制AQP0界面上的液体和蛋白质本身的图谱。利用AFM悬臂梁的基本征模成像，主要探测膜表面的界面水。结果突出了围绕AQP0四聚体的一个明确的区域，在那里水对蛋白质表现出更高的亲和力。第二本征模的成像由蛋白质的机械响应主导，并提供蛋白质表面和亚表面结构的亚分子细节。文中还研究了模式与谐波之间的关系。
Aquaporins are integral membrane proteins that regulate the transport of water and small molecules in and out of the cell. In eye lens tissue, circulation of water, ions and metabolites is ensured by a microcirculation system in which aquaporin-0 (AQP0) plays a central role. AQP0 allows water to flow beyond the diffusion limit through lens membranes. AQP0 naturally arranges in a square lattice. The malfunction of AQP0 is related to numerous diseases such as cataracts. Despite considerable research into its structure, function and dynamics, the interface between the protein and the surrounding liquid and the effect of the lattice arrangement on the behaviour of water at the interface with the membrane are still not fully understood. Here we use a multifrequency atomic force microscopy (AFM) approach to map both the liquid at the interface with AQP0 and the protein itself with sub-nanometer resolution. Imaging using the fundamental eigenmode of the AFM cantilever probes mainly the interfacial water at the surface of the membrane. The results highlight a well-defined region that surrounds AQP0 tetramers and where water exhibits a higher affinity for the protein. Imaging in the second eigenmode is dominated by the mechanical response of the protein and provides sub-molecular details of the protein surface and the sub-surface structure. The relationship between modes and harmonics is also examined.