Department of Physics, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments and School of Mechanical Engineering, Southeast University , Nanjing 210096, China.
ACS Nano. 2017 Jul 25;11(7):7091-7100. doi: 10.1021/acsnano.7b02718. Epub 2017 Jul 13.
Single-molecule studies of protein folding hold keys to unveiling protein folding pathways and elusive intermediate folding states-attractive pharmaceutical targets. Although conventional single-molecule approaches can detect folding intermediates, they presently lack throughput and require elaborate labeling. Here, we theoretically show that measurements of ionic current through a nanopore containing a protein can report on the protein's folding state. Our all-atom molecular dynamics (MD) simulations show that the unfolding of a protein lowers the nanopore ionic current, an effect that originates from the reduction of ion mobility in proximity to a protein. Using a theoretical model, we show that the average change in ionic current produced by a folding-unfolding transition is detectable despite the orientational and conformational heterogeneity of the folded and unfolded states. By analyzing millisecond-long all-atom MD simulations of multiple protein transitions, we show that a nanopore ionic current recording can detect folding-unfolding transitions in real time and report on the structure of folding intermediates.
单分子研究蛋白质折叠揭示蛋白质折叠途径和难以捉摸的中间折叠状态——有吸引力的药物靶点。虽然传统的单分子方法可以检测折叠中间体，但目前它们缺乏通量，并且需要精细的标记。在这里，我们从理论上表明，通过含有蛋白质的纳米孔测量离子电流可以反映蛋白质的折叠状态。我们的全原子分子动力学 (MD) 模拟表明，蛋白质的展开会降低纳米孔离子电流，这种效应源于离子在接近蛋白质时的迁移率降低。使用理论模型，我们表明，尽管折叠态和展开态的取向和构象异质性，由折叠-展开转变产生的平均离子电流变化是可检测的。通过分析多个蛋白质转变的毫秒级全原子 MD 模拟，我们表明纳米孔离子电流记录可以实时检测折叠-展开转变，并报告折叠中间体的结构。
