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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A functional single-molecule binding assay via force spectroscopy
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A functional single-molecule binding assay via force spectroscopy

机译:通过力能谱进行功能性单分子结合测定

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Protein-ligand interactions, including protein-protein interactions, are ubiquitously essential in biological processes and also have important applications in biotechnology. A wide range of methodologies have been developed for quantitative analysis of protein-ligand interactions. However, most of them do not report direct functional/structural consequence of ligand binding. Instead they only detect the change of physical properties, such as fluorescence and refractive index, because of the colocalization of protein and ligand, and are susceptible to false positives. Thus, important information about the functional state of protein-ligand complexes cannot be obtained directly. Here we report a functional single-molecule binding assay that uses force spectroscopy to directly probe the functional consequence of ligand binding and report the functional state of protein-ligand complexes. As a proof of principle, we used protein G and the Fc fragment of IgG as a model system in this study. Binding of Fc to protein G does not induce major structural changes in protein G but results in significant enhancement of its mechanical stability. Using mechanical stability of protein G as an intrinsic functional reporter, we directly distinguished and quantified Fc-bound and Fc-free forms of protein G on a single-molecule basis and accurately determined their dissociation constant. This single-molecule functional binding assay is label-free, nearly background-free, and can detect functional heterogeneity, if any, among protein-ligand interactions. This methodology opens up avenues for studying protein-ligand interactions in a functional context, and we anticipate that it will find broad application in diverse protein-ligand systems.
机译:蛋白质-配体相互作用,包括蛋白质-蛋白质相互作用,在生物过程中无处不在,并且在生物技术中也具有重要的应用。已经开发出用于定量分析蛋白质-配体相互作用的多种方法。然而,它们中的大多数没有报道配体结合的直接功能/结构后果。相反,由于蛋白质和配体的共定位作用,它们仅检测物理性质的变化,例如荧光和折射率,并且容易受到假阳性的影响。因此,不能直接获得有关蛋白质-配体复合物功能状态的重要信息。在这里,我们报告功能单分子结合测定,使用力谱直接探测配体结合的功能后果,并报告蛋白质-配体复合物的功能状态。作为原理的证明,我们在本研究中使用蛋白G和IgG的Fc片段作为模型系统。 Fc与蛋白G的结合不会引起蛋白G的主要结构变化,但会导致其机械稳定性显着提高。使用蛋白G的机械稳定性作为内在的功能性报告基因,我们直接在单分子基础上对蛋白G的Fc结合形式和无Fc形式进行了区分和定量,并准确确定了它们的解离常数。这种单分子功能结合测定无需标签,几乎没有背景,并且可以检测蛋白质-配体相互作用中的功能异质性(如果有)。这种方法学为在功能范围内研究蛋白质-配体相互作用开辟了途径,我们预计它将在各种蛋白质-配体系统中得到广泛的应用。

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