Related Experiment Videos
Semisynthesis of horse heart cytochrome c analogues from two or three fragments
Insights
Researchers created modified horse heart cytochrome c proteins. These analogues retained electron transfer capabilities, showing altered reaction rates and redox potentials, offering insights into protein function and structure.
Area of Science:
- Biochemistry
- Protein Chemistry
- Electron Transfer
Background:
- Cytochrome c is a crucial protein in cellular respiration.
- Understanding its structure-function relationship is key to cellular energy production.
Purpose of the Study:
- To synthesize and characterize analogues of horse heart cytochrome c.
- To investigate the impact of specific amino acid substitutions on electron transfer and redox properties.
Main Methods:
- Chemical cleavage of horse heart cytochrome c using cyanogen bromide.
- Semisynthesis and total organochemical synthesis of cytochrome c fragments and analogues.
- Condensation of peptide fragments to form covalently recombined analogous cytochromes c.
- Assays to measure electron retention, transfer to cytochrome c oxidase, reaction rates, and Michaelis constants.
- Determination of redox potentials.
Main Results:
- Successfully synthesized four analogues of cytochrome c-(66-104).
- Covalently recombined analogues retained electron transfer function.
- Analogues exhibited varied reaction rates and Michaelis constants compared to native cytochrome c.
- Amino acid substitutions (Tyr67----Phe, Thr78----Val, Phe82----Leu, Tyr97----Leu) significantly altered redox potentials.
Conclusions:
- Specific amino acid residues in cytochrome c critically influence its redox potential and electron transfer efficiency.
- Synthetic approaches allow for the creation of functional cytochrome c analogues with tunable properties.
- This study provides valuable structure-function insights into cytochrome c's role in the electron transport chain.
Abstract:
Horse heart cytochrome c was cleaved with cyanogen bromide. The largest fragment, [Hse65]cytochrome c-(1-65)-pentahexacontapeptide lactone, was used in condensations involving four analogues of the complementary cytochrome c-(66-104)-nonatriacontapeptide. Two of the latter compounds were obtained from a semisynthesis starting with a partially protected fragment N epsilon 86-88,99,100-penta(methylsulfonylethyloxycarbonyl)cytochrome c-(81-104)-tetracosapeptide (also arising from a cyanogen bromide-mediated degradation) and analogues of the middle part, cytochrome c-(66-80)-pentadecapeptide, which were prepared by organochemical synthesis. Two other analogues of the cytochrome c-(66-104)-nonatriacontapeptide were prepared entirely by organochemical synthesis. Each of the covalently recombined analogous cytochromes c could retain an electron in the presence of oxygen and transfer it to cytochrome c oxidase, although with different reaction rates and Michaelis constants. Their redox potentials varied over a broad range. The exchanges Tyr67----Phe(F) and Thr78----Val gave rise to analogues with a lower redox potential than native cytochrome c, while the exchange Phe82----Leu or Tyr97----Leu led to analogues with the same and a higher redox potential, respectively.