On the redox conformational change in cytochrome c

Area of Science:

• Biochemistry
• Structural Biology
• Protein Dynamics

Background:

• Cytochrome c is a crucial protein in electron transport chains.
• Understanding its structural dynamics is key to elucidating its function.
• Previous studies on cytochrome c-cytochrome c peroxidase complexes provide context.

Purpose of the Study:

• To reexamine the crystal structures of oxidized and reduced tuna cytochrome c.
• To correlate structural changes with binding affinity and electron transfer mechanisms.
• To propose a model for cytochrome c's function as an electron storage/transfer machine.

Main Methods:

• Superposition of crystal structures of oxidized and reduced tuna cytochrome c.
• Analysis of structural changes, including amino acid residue motion (e.g., lysine-27).
• Investigation of heme group conformational changes and interactions within the protein envelope.

Main Results:

• Observed structural changes align with previously suggested binding faces from chemical modification studies.
• Distinct motions of lysine-27 and binding edges suggest a redox binding-affinity switch mechanism.
• Internal heme conformational changes and charge redistribution drive protein conformational changes and heme tilting.

Conclusions:

• Tuna cytochrome c functions as an electron storage/transfer machine.
• The molecule comprises three key modules: binding, electron storage, and conformational energy storage.
• Structural dynamics, particularly heme movement, are integral to its redox activity and binding affinity.