How does the cell open and close electron taps?
Researchers at the Institute for Bioengineering of Catalonia (IBEC) have achieved a nanoscale view of the electron transport between redox partner proteins of the respiratory chain, allowing for a better understanding of their regulation by phosphorylation.
Mitochondria play a key role in cellular energy production. They are membrane-bound cell organelles found in almost all eukaryotic cells (animals, plants, and fungi). Their main function in animal cells is to convert nutrients into chemical energy, stored in the form of adenosine triphosphate molecules, through a process called cellular respiration, which includes a tightly regulated electron transport chain. In addition to this function, mitochondria are also responsible for other functions, such as inducing cell death in response to stress events. How does the cell open and close the "taps" that control electron transport through these processes?
A previous study by IBEC demonstrated that the transfer of electrons between mitochondrial proteins cytochrome c and cytochrome bc1takes place at a distance through the aqueous solution, via a charge conduit established between them. This new study reveals how this process is regulated by phosphorylation (addition of a phosphate group near the redox active site of cytochrome c).
The researchers combined the analysis of electron transport at the molecular level with the measurement of protein-protein interaction forces, leading to a better understanding of the effects of cytochrome c phosphorylation on the molecular regulation of the mitochondrial respiratory chain. They discovered that phosphorylation impairs electron transport by disrupting the charge conduit and increasing the affinity between cytochrome c and cytochrome bc1, thus leading to the formation of bottlenecks in the process, and slowing the flow of electrons in the chain.
These results also highlight the biological relevance of long-distance charge transport between redox proteins through the aqueous solution and contribute to the understanding of interprotein electron transfer.