Liquid-Liquid Phase Separation Modifies the Dynamic Properties of Intrinsically Disordered Proteins

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• Membraneless organelles form via liquid-liquid phase separation (LLPS) of flexible biomolecules.
• LLPS is crucial for organizing cellular processes within these organelles.

Purpose of the Study:

• To investigate the dynamic properties of intrinsically disordered proteins during LLPS at atomic resolution.
• To compare protein dynamics in dilute and dense phases relevant to membraneless organelles.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy, specifically 15N NMR relaxation at varying magnetic field strengths.
• Molecular dynamics (MD) simulations under self-crowding conditions.

Main Results:

• Protein dynamics across all detectable timescales (librational, dihedral, segmental) are significantly slowed in the dense phase.
• Slower, chain-like motions become dominant in the dense phase, altering the dynamic profile.
• MD simulations correlate reduced backbone dynamics with increased intermolecular contacts and reduced conformational space in crowded conditions.

Conclusions:

• LLPS profoundly alters protein dynamics, slowing motions and favoring slower, chain-like dynamics.
• These dynamic changes are critical for the function and organization within membraneless organelles.
• The study provides mechanistic insights into LLPS-driven changes in protein behavior.