Cytochrome c reconstituted from two peptide fragments displays native-like redox properties.

The research paper discusses an experiment where two fragments of horse cytochrome c are recombined, exhibiting mostly similar but slightly less stable chemical properties compared to the original protein. The difference in stability is credited to slight disturbances in the protein’s structure, although the protein still maintains its fundamental function of transferring electrons.

Understanding Cytochrome c

• Cytochrome c is a small protein found in almost all living cells, primarily within the mitochondria.
• It plays a key role in the electron transport chain, facilitating the transport of electrons during the process of creating adenosine triphosphate (ATP), the main energy source for metabolic functions.

The Experiment

• In the experiment, the researchers split a horse cytochrome c protein into two fragments (N-fragment, residues 1-56, and C-fragment, residues 57-104).
• They then recombined these fragments, creating a 1:1 fragment complex with a compact conformation.

Observations and Findings

• The researchers found that this recombined protein had recovered the alpha helical structure and the native Met80-Fe(III) axial bond, similar to a complete cytochrome c protein.
• The ferric complex showed a less rigid atomic packing and a decreased stability when compared to the original protein, suggesting perturbations involving the Trp59 microenvironment and, to a lesser extent, the heme pocket region.
• The recombined protein also showcased a redox potential near-identical to the intact protein, indicating recovery of the native Met80-heme Fe(III) axial bond.

Conclusions

• Despite the decreased stability and structural disturbances, the recombined protein demonstrated reactivity similar to a complete cytochrome c protein in its reaction with cytochrome c oxidase.
• The researchers thus concluded that while the absence of some native cross-links and the interlocked packing impacted the rigidity and stability of the protein, the native redox properties remained largely unaffected, provided that certain structural elements were preserved.