Detection of Mutation-Induced Conformational Changes in an Intrinsically Disordered Protein by Double Quantum Coherence Electron Spin Resonance Methodology
A. S. Roy, K. Tsay, P. P. Borbat, A. Destefano, S. Han, M. Srivastava, J. H. Freed. J. Am. Chem. Soc., 2026, 148, 2378-2387. https://doi.org/10.1021/jacs.5c16298
Corrections J. Am. Chem. Soc. 2026, 148, 8, 9140,. https://doi.org/10.1021/jacs.6c02082
Intrinsically disordered proteins (IDPs) underlie essential cellular functions and drive neurodegenerative diseases through mutation-induced structural changes, yet their conformational heterogeneity often evades crystallography and cryo-EM. Electron spin resonance (ESR) pulsed dipolar spectroscopy (PDS), which determines distance distributions between a pair of spin-labeled residues in a protein, can provide complementary and meaningful information related to conformational heterogeneity in IDPs. Double quantum coherence (DQC) is an important ESRPDS technique, capable of measuring a wide range of distances(∼10toat least80Å), and is a single-frequency technique with a small back ground that can be easily removed. This makes DQC an ideal candidate to probe IDPs. We present a complete theoretical framework for DQC data analysis, incorporating pseudo-secular dipolar coupling and finite pulse effects, enabling rapid and accurate reconstruction of complex distance distributions in doubly nitroxide-labeled IDPs. We validate the method on rigid biradicals with known inter-spin distances. The application to a tau protein fragment(jR2R3) reveals distinct end-to-end distance distributions for the wild-type vs the disease-associatedP301Lmutant. The results expose differences in their conformationaldistributions,whichlikelygoverntheirdivergentaggregationpropensities.ThisadvancealsoestablishesDQCESR as a powerful, accessible tool for probing disorders in biomolecular systems.