Membrane binding induces destabilization of cytochrome c structure

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Cytochrome c is a vital protein involved in electron transport.
• Understanding protein-membrane interactions is crucial for cellular processes.
• Acidic phospholipids play key roles in membrane protein association.

Purpose of the Study:

• To investigate the impact of phospholipid membrane binding on ferricytochrome c structure and stability.
• To elucidate the role of acidic phospholipids in mediating these changes.
• To explore the generalizability of these findings to other water-soluble proteins.

Main Methods:

• Fourier-transform infrared spectroscopy (FTIR) to analyze protein secondary structure.
• Differential scanning calorimetry (DSC) to assess protein thermal stability.
• Hydrogen-deuterium exchange to probe protein tertiary structure accessibility.

Main Results:

• Membrane binding caused minimal changes to ferricytochrome c secondary structure.
• Significant increase in hydrogen-deuterium exchange indicated tertiary structure loosening.
• Thermodynamic stability decreased, with denaturation temperature dropping ~30°C upon binding to acidic phospholipid membranes (DMPG, DOPG).
• Structural perturbation correlated with the surface density of acidic phospholipids.

Conclusions:

• Acidic phospholipids induce conformational changes and destabilize ferricytochrome c tertiary structure.
• Lipid-mediated destabilization may be a general mechanism for electrostatic membrane-binding proteins.
• This interaction could influence protein function and cellular signaling.