Nanosecond Molecular Motion in pHP1α Liquid-Liquid Phase Separation Captured by Solid-State NMR.

Area of Science:

• Biophysics
• Structural Biology
• Molecular Dynamics

Background:

• Protein structure, function, and dynamics are key to biological activity, especially in complex systems.
• Nuclear Magnetic Resonance (NMR) spectroscopy is vital for studying molecular motion across timescales.
• Phase-separated systems, like phosphorylated heterochromatin protein 1 alpha (pHP1α), present unique challenges due to their mixed solid- and solution-like properties.

Purpose of the Study:

• To investigate the nanosecond molecular motions within pHP1α liquid-liquid phase separation (LLPS).
• To characterize the site-specific global dynamics of pHP1α during LLPS.
• To understand the relationship between protein dynamics and chromatin organization.

Main Methods:

• Utilized relaxation in hetNOE-filtered heteronuclear single quantum coherence (HSQC) signals to probe nanosecond dynamics.
• Systematically analyzed motions using both hetNOE-filtered HSQC and conventional HSQC techniques.
• Focused on site-specific analysis of molecular motion in pHP1α LLPS.

Main Results:

• Identified approximately 15 nanosecond (ns) timescale motions in the pHP1α LLPS system.
• Revealed evidence for the coexistence of different dynamic phases within pHP1α LLPS.
• Findings align with and support previous observations regarding pHP1α's role in chromatin organization.

Conclusions:

• The study elucidates the complex nanosecond dynamics of pHP1α during LLPS.
• The detected motions suggest a heterogeneous dynamic environment within the phase-separated state.
• This research enhances understanding of biomolecular phase separation, chromatin compaction, and genomic stability.