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Modulation of Fluorescent Protein Chromophores To Detect Protein Aggregation with Turn-On Fluorescence

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journal contribution
posted on 08.06.2018 by Yu Liu, Charles H. Wolstenholme, Gregory C. Carter, Hongbin Liu, Hang Hu, Leeann S. Grainger, Kun Miao, Matthew Fares, Conner A. Hoelzel, Hemant P. Yennawar, Gang Ning, Manyu Du, Lu Bai, Xiaosong Li, Xin Zhang
We present a fluorogenic method to visualize misfolding and aggregation of a specific protein-of-interest in live cells using structurally modulated fluorescent protein chromophores. Combining photophysical analysis, X-ray crystallography, and theoretical calculation, we show that fluorescence is triggered by inhibition of twisted-intramolecular charge transfer of these fluorophores in the rigid microenvironment of viscous solvent or protein aggregates. Bioorthogonal conjugation of the fluorophore to Halo-tag fused protein-of-interests allows for fluorogenic detection of both misfolded and aggregated species in live cells. Unlike other methods, our method is capable of detecting previously invisible misfolded soluble proteins. This work provides the first application of fluorescent protein chromophores to detect protein conformational collapse in live cells.