基于DNA折纸的单个链霉亲和素分子的原子力显微术高分辨成像

High-resolution imaging of single-molecule streptavidin using atomic force microscopy based on DNA origami

链霉亲和素(Streptavidin,STV)和生物素(Biotin)之间的非共价相互作用很强,已被运用到包括分子生物学、免疫学以及生物技术领域。STV与Biotin间优异的结合能力与其结构密切相关,晶体解析结果证明STV是一个四聚体蛋白。原子力显微镜技术(Atomic Force Microscopy,AFM)可以在液体环境下获得生物单分子的形貌信息,对结构和功能的研究具有非常重要的作用。然而,由于STV分子小而柔软,获得高分辨的AFM图像极其困难。本研究利用DNA折纸可寻址的特点,将Biotin定位修饰在折纸上,选择性地将STV固定在折纸设定的位置上,实现了对单个STV分子的高分辨成像,观察到了单个STV呈"沙漏形"结构,与其晶体结构符合性较好。同时,我们注意到STV形貌易受成像力的影响,可能与STV分子的柔性相关。这种基于DNA折纸的高分辨成像方法,简单、方便,为研究生物分子形貌和功能提供了新思路。

[Background] The strong non-covalent interaction between streptavidin (STV) and biotin has been applied to various fields including molecular biology, immunology and biotechnology. The unique binding ability of STV to biotin is closely related to its structure. The crystal analysis results show that STV is a tetramer protein. Atomic force microscopy (AFM) plays an important role in studying the structure and function of proteins because it can provide morphological information of individual biomolecules in liquid environment. However, resolving STV with high-resolution AFM imaging remains challenge due to the small size and soft property.[Purpose] This study aims to obtain high resolution single molecule STV images by AFM.[Methods] With modified biotin location on DNA origami, the addressable DNA origami was employed to selectively fix STVs. Then, AFM was used for image processing of STVs.[Results] The single-molecule STV image at high-resolution was obtained. The observed STV showed an "hourglass-shaped" structure which consisted well with its crystal structure. At the same time, we noted that the STV morphology was susceptible to the effect of the loading force, indicating that it may be related to the flexibility of STVs.[Conclusion] The simple and convenient method will provide a new way for studying the morphology and function of biomolecules.