Plasticity of intermediate filament subunits.

Area of Science:

• Biochemistry
• Cell Biology
• Structural Biology

Background:

• Intermediate filaments (IFs) are crucial cytoskeletal components assembled from soluble protein subunits.
• Previous imaging methods like electron microscopy often presented IF subunits as straight rods due to sample preparation artifacts.

Purpose of the Study:

• To investigate the conformational plasticity of vimentin, desmin, and keratin IF subunits.
• To explore how various conditions influence the shape and assembly of IF subunits.

Main Methods:

• Atomic Force Microscopy (AFM) and cryo-electron microscopy (cryo-EM) with cryo-negative staining.
• Molecular modeling and coarse-grained molecular dynamics simulations of vimentin tetramers.

Main Results:

• IF subunits were visualized as thin, slightly curved rods, but also formed aggregates under cryo-EM negative staining.
• AFM revealed a mixture of extended and compact subunit conformations on mica.
• Divalent ions (Ca2+, Mg2+) and glutaraldehyde promoted compact conformations.

Conclusions:

• IF subunits display significant conformational plasticity, switching between extended and compact states.
• Environmental factors critically influence IF subunit conformation and potentially assembly dynamics.