Exploring the stability limits of actin and its suprastructures

Area of Science:

• Cell Biology
• Biophysics
• Structural Biology

Background:

• Actin forms the cell's microfilament system in globular (G-actin) and filamentous (F-actin, B-actin) states.
• Understanding actin stability is crucial for cell structure and function, especially under extreme conditions.

Purpose of the Study:

• To investigate the temperature and pressure stability of G-, F-, and B-actin.
• To elucidate the forces stabilizing actin self-assembly.
• To explain the in vivo pressure sensitivity of actin assembly.

Main Methods:

• Fourier transform infrared spectroscopy
• Differential scanning and pressure perturbation calorimetry
• Small-angle X-ray scattering
• Laser confocal scanning microscopy
• Transmission electron microscopy

Main Results:

• G-actin is the least stable form, with limited stability below 1 kbar and 1-4°C.
• Actin assemblies (F-actin, B-actin) are stable under many extreme Earth conditions.
• Filamentous structures disassemble beyond 3-4 kbar, with complete dissociation above 4 kbar.
• Disordering of actin assemblies begins between 1-2 kbar, correlating with in vivo observations.

Conclusions:

• The limited pressure stability of monomeric G-actin likely suppresses actin assembly at high pressures.
• Actin supramolecular structures exhibit remarkable stability under extreme environmental conditions.
• This study provides insights into actin's behavior in diverse environments, from cellular to abyssal.