The interaction of ferrocytochrome c with long-chain fatty acids and their CoA and carnitine esters.

The study investigates the interaction of ferrocytochrome c with various fatty acids and their derivatives, determining that a minimum chain length of 14 carbons is required for significant interaction, and that this interaction can disrupt the S-Fe coordination in the protein’s structure.

Interaction of Ferrocytochrome c with Fatty Acids

• The primary goal of the research was to examine how different types of fatty acids interact with horse heart ferrocytochrome c. This was done to determine the potential implications for electron transport and energy metabolism.
• In the study, the team compared different fatty acids, noting that significant effects on the ferroheme chromophore and major changes in electronic spectra required a minimum chain length of 14 carbons.

Less Strong Interactions with Coenzyme A and Carnitine Esters

• Beyond fatty acids, the researchers also explored the interaction of ferrocytochrome c with coenzyme A and carnitine esters. These compounds were found to interact less strongly than fatty acids.
• Long-chain alcohols, another group of compounds, were found not to interact with the protein at all.

Saturable Binding Site and Stoichiometry

• The study found a single, saturable fatty acid binding site on the protein, with different methods of measurement yielding similar dissociation constants for oleate binding (around 23.1-30 microM).
• The binding stoichiometry, which indicates the ratio of fatty acid to protein in the complex, was found to be 1:1.

Disruption of S-Fe Coordination

• The study provides evidence (from electronic spectra and proton nuclear magnetic resonance analysis) that the binding of a ligand disrupts the S-Fe coordination (involving methionine 80) in the protein’s structure.

Identification of a Potential Binding Channel

• Further findings of the study, supported by molecular modeling, led to the identification of a putative binding channel for fatty acids in the protein, which is located between lysines 72 and 73.