Cytochrome c Complexes with Cardiolipin Monolayer Formed under Different Surface Pressure

Area of Science:

• Mitochondrial biophysics
• Apoptosis signaling pathways
• Protein-lipid interactions

Background:

• The complex of cytochrome c (Cytc) and cardiolipin (CL) is critical for apoptosis.
• Existing models propose Cytc binds to the bilayer surface or forms hydrophobic nanoparticles.

Purpose of the Study:

• To investigate the interaction between Cytc and CL monolayers.
• To bridge the gap between existing structural models of the Cytc-CL complex.

Main Methods:

• Studied Cytc interaction with Langmuir monolayers of CL.
• Analyzed surface pressure changes and surface area-surface pressure isotherms.
• Investigated protein-lipid film behavior during compression-expansion cycles.

Main Results:

• Cytc binding to CL monolayers followed a pseudo-first-order rate.
• Conformational transition of Cytc was observed, creating "stratified" protein with hydrophobic and hydrophilic regions.
• Ethanol accelerated Cytc adsorption, and hysteresis loops indicated conformational changes.

Conclusions:

• Cytc undergoes a conformational transition upon interaction with CL monolayers.
• This stratification may lead to membrane folding, pore formation, or reactive "bubbles" within bilayers.
• The findings offer insights into Cytc-CL's role in apoptosis and lipid peroxidation.