Detection of Mutation-Induced Conformational Changes in an Intrinsically Disordered Protein by Double Quantum...

Area of Science:

• Biophysics
• Structural Biology
• Neuroscience

Background:

• Intrinsically disordered proteins (IDPs) are crucial for cellular functions but implicated in neurodegenerative diseases.
• Conformational heterogeneity in IDPs poses challenges for traditional structural biology techniques like crystallography and cryo-electron microscopy.
• Electron spin resonance (ESR) pulsed dipolar spectroscopy (PDS) offers a complementary approach to study IDP dynamics.

Purpose of the Study:

• To develop and validate a robust theoretical framework for analyzing double quantum coherence (DQC) ESR PDS data.
• To apply the DQC ESR method to investigate conformational differences in intrinsically disordered proteins, specifically the tau protein.
• To establish DQC ESR as an accessible and powerful tool for probing biomolecular disorder.

Main Methods:

• Development of a complete theoretical framework for DQC data analysis, including pseudosecular dipolar coupling and finite pulse effects.
• Validation of the DQC analysis method using rigid biradicals with known interspin distances.
• Application of DQC ESR to a tau protein fragment (jR2R3), comparing wild-type and P301L mutant forms.

Main Results:

• The developed DQC ESR framework enables rapid and accurate reconstruction of complex distance distributions in doubly nitroxide-labeled IDPs.
• Distinct end-to-end distance distributions were observed between the wild-type tau fragment and the P301L mutant.
• These conformational differences correlate with divergent aggregation propensities, offering insights into disease mechanisms.

Conclusions:

• The advanced DQC ESR technique provides a powerful and accessible means to characterize conformational heterogeneity in IDPs.
• The study demonstrates significant conformational differences in tau protein variants, relevant to neurodegenerative disease.
• DQC ESR is established as a valuable tool for studying disordered biomolecular systems and their functional implications.