Structure and Elasticity of Mitochondrial Membranes: A Molecular Dynamics Simulation Study

Area of Science:

• Cell Biology
• Biophysics
• Biochemistry

Background:

• Mitochondria, the cell's powerhouse, generate ATP and regulate vital processes like apoptosis and calcium homeostasis.
• Mitochondrial structure and dynamic shape changes highlight the importance of their mechanical properties for cellular functions.

Purpose of the Study:

• To investigate the molecular-level structure and mechanical properties of inner and outer mitochondrial membranes.
• To understand how lipid composition, including cardiolipin and cholesterol, and membrane asymmetry affect mitochondrial membrane mechanics.

Main Methods:

• Atomistic molecular dynamics simulations were performed on six mitochondrial membrane models.
• Simulations analyzed variations in cardiolipin and cholesterol concentrations and leaflet symmetry.
• Calculated structural quantities and elastic moduli (bending, twisting, tilting) for the membrane models.

Main Results:

• Inner and outer mitochondrial membrane structures are similar and largely independent of lipid composition variations.
• Membrane bending modulus increases with higher cardiolipin or cholesterol concentrations.
• Membrane bending modulus decreases with increased membrane asymmetry; dipole potential rises with cardiolipin concentration.

Conclusions:

• Cardiolipin and cholesterol significantly influence mitochondrial membrane mechanics, particularly bending stiffness.
• Membrane asymmetry negatively impacts bending modulus.
• Cardiolipin's role in ion/proton transport and maintaining mitochondrial cristae structure is suggested.