The Magic of Linking Rings: Discovery of a Unique Photoinduced Fluorescent Protein Crosslink

Posted on 14.05.2022 - 12:03
Fluorosubstituted tryptophans serve as valuable probes for fluorescence and nuclear magnetic resonance (NMR) studies of proteins. Here, we describe an unusual photoreactivity introduced by replacing the single tryptophan in cyclophilin A with 7-fluoro-tryptophan. UV exposure at 282 nm defluorinates 7-fluoro-tryptophan and crosslinks it to a nearby phenylalanine, generating a bright fluorophore. The crosslink-containing fluorescent protein possesses a large quantum yield of ∼0.40 with a fluorescence lifetime of 2.38 ns. The chemical nature of the crosslink and the three-dimensional protein structure were determined by mass spectrometry and NMR spectroscopy. To the best of our knowledge, this is the first report of a Phe–Trp crosslink in a protein. Our finding may break new ground for developing novel fluorescence probes and for devising new strategies to exploit aromatic crosslinks in proteins.

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Lu, Manman; Toptygin, Dmitri; Xiang, Yufei; Shi, Yi; Schwieters, Charles D.; Lipinski, Emma C.; et al. (2022): The Magic of Linking Rings: Discovery of a Unique Photoinduced Fluorescent Protein Crosslink. ACS Publications. Collection. https://doi.org/10.1021/jacs.2c02054
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