Intramolecular structural heterogeneity altered by long-range contacts in an intrinsically disordered protein

Area of Science:

• Biophysics
• Structural Biology
• Polymer Physics

Background:

• Structured proteins fold via short- and long-range interactions, dictating function.
• Intrinsically disordered proteins (IDPs) comprise ~40% of the eukaryotic proteome and exist in dynamic conformational ensembles.
• Understanding IDP structure-function relationships requires correlating sequence with ensemble statistics.

Purpose of the Study:

• To investigate the intramolecular structural heterogeneity of the neurofilament low intrinsically disordered tail domain (NFLt).
• To correlate the amino acid sequence of NFLt with its structural ensemble statistics.
• To assess the applicability of polymer physics theories in describing IDP conformational dynamics.

Main Methods:

• Small-angle X-ray scattering (SAXS) to probe protein structure.
• Time-resolved Förster resonance energy transfer (trFRET) to measure intramolecular distances.
• Application of polymer physics models, including Flory scaling theory.

Main Results:

• Flory scaling exponent of NFLt subsegments linearly correlates with net charge, indicating a transition from ideal to self-avoiding chain statistics.
• NFLt segments exhibit more expanded structural statistics in the whole protein context compared to independent measurements.
• Long-range contacts between distant amino acids significantly influence the overall intramolecular structure of NFLt.

Conclusions:

• Polymer physics provides a partial framework for linking IDP sequence to conformational ensembles.
• Long-range interactions are critical determinants of intramolecular structure in IDPs.
• Advanced polymer theories are necessary for comprehensive modeling of IDP ensembles and their biological functions.