Comprehensive Regulation of Liquid-Liquid Phase Separation of Polypeptides

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Liquid-liquid Phase Separation (LLPS) of proteins and nucleic acids is vital for cellular functions and implicated in diseases.
• Understanding the molecular drivers of LLPS is essential for biological insight and therapeutic development.

Purpose of the Study:

• To investigate the regulation of LLPS in proline-arginine (PR) peptides by varying peptide length and salt concentration.
• To identify the specific molecular forces, including hydrophobicity and electrostatics, that drive peptide LLPS.

Main Methods:

• Systematic modification of repetitive PR peptide lengths.
• Alteration of solution salt concentrations and dielectric constant using ethyl alcohol and 6-Aminocaproic acid.
• Introduction of hydrophobic disruptors like 1,6-hexanediol.

Main Results:

• A threshold of eight PR repeats was identified, requiring higher salt concentrations for LLPS.
• Ethyl alcohol enhanced LLPS of PR15 by intensifying electrostatic interactions, while 6-Aminocaproic acid inhibited it.
• Hydrophobicity and electrostatic interactions were found to conjointly drive LLPS in these peptide systems.

Conclusions:

• Peptide length and solution conditions significantly regulate LLPS.
• LLPS is driven by a combination of hydrophobic and electrostatic forces.
• Findings offer guidance for manipulating LLPS in other peptide/protein systems and addressing related diseases.