Mapping\nFull Conformational Transition Dynamics of\nIntrinsically Disordered Proteins Using a Single-Molecule Nanocircuit

Intrinsically\ndisordered proteins (IDPs) are emerging therapeutic\ntargets for human diseases. However, probing their transient conformations\nremains challenging because of conformational heterogeneity. To address\nthis problem, we developed a biosensor using a point-functionalized\nsilicon nanowire (SiNW) that allows for real-time sampling of single-molecule\ndynamics. A single IDP, N-terminal transactivation domain of tumor\nsuppressor protein p53 (p53<sub>TAD1</sub>), was covalently conjugated\nto the SiNW through chemical engineering, and its conformational transition\ndynamics was characterized as current fluctuations. Furthermore, when\na globular protein ligand in solution bound to the targeted p53<sub>TAD1</sub>, protein–protein interactions could be unambiguously\ndistinguished from large-amplitude current signals. These proof-of-concept\nexperiments enable semiquantitative, realistic characterization of\nthe structural properties of IDPs and constitute the basis for developing\na valuable tool for protein profiling and drug discovery in the future.