Activation of Cytochrome C Peroxidase Function Through Coordinated Foldon Loop Dynamics upon Interaction with Anionic...

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Cardiolipin (CL) is a key mitochondrial lipid regulating apoptosis.
• Cytochrome c (cyt c) peroxidase activity is crucial for apoptosis signaling.
• Molecular mechanisms of CL and other anionic lipids in cyt c activation are unclear.

Purpose of the Study:

• To investigate how cardiolipin (CL) and phosphatidylglycerol (PG) activate cytochrome c (cyt c) peroxidase activity.
• To correlate functional differences with structural and motional changes in membrane-associated cyt c.
• To elucidate the role of protein-lipid interactions in mitochondrial apoptosis.

Main Methods:

• Magic angle spinning solid-state NMR spectroscopy for structural and motional studies of cyt c.
• Mass spectrometry to assay lipid peroxidase activity.
• Comparative analysis of cyt c activation by CL and PG.

Main Results:

• PG binding to cyt c results in a nativelike fold with significant, albeit lower, peroxidase activity compared to CL.
• Lipid-specific differences in peroxidase activation correlate with altered protein mobility in specific segments.
• CL binding upregulates dynamics in omega loops C and D, controlled by protein:lipid stoichiometry.
• Membrane-induced cyt c destabilization affects specific foldons, preserving stable helices.

Conclusions:

• Lipid-specific dynamics and structural changes in cyt c govern its peroxidase activity.
• Protein-lipid stoichiometry plays a critical role in regulating cyt c dynamics and function.
• These findings illuminate the interplay of protein and lipid dynamics in apoptosis-related proteolipid complexes.