From the Research
The proton motive force will be decreased, but to a value greater than zero. When malate is oxidized by the electron transport chain in the mitochondria, protons are pumped from the matrix to the intermembrane space, creating a proton gradient (the proton motive force) across the inner mitochondrial membrane. This force has two components: a pH gradient and an electrical potential.
- The proton motive force is crucial for the production of ATP by ATP synthase.
- The electrical potential component is generated by the movement of electrons through the electron transport chain.
- The pH gradient component is generated by the pumping of protons across the inner mitochondrial membrane.
When valinomycin is added with potassium, it allows K+ ions to freely move across the inner mitochondrial membrane following their concentration gradient.
- As K+ ions enter the matrix, they partially dissipate the electrical component of the proton motive force by neutralizing some of the charge separation 1.
- However, valinomycin specifically affects the electrical potential component without directly affecting the pH gradient component.
- Therefore, while the overall proton motive force decreases due to the reduction in electrical potential, it doesn't drop to zero because the pH gradient component remains largely intact.
The most recent and highest quality study on this topic is from 2019, which discusses the mechanism of valinomycin-induced ion transport across model lipid bilayer membranes 2.
- This study provides new insights into the ionophore mechanism of valinomycin and its effects on the proton motive force.
- The study suggests that valinomycin transports ions across the membrane by creating a complex with potassium ions and forming an ion pair with a counter anion.
- The ion pair resides within the hydrophobic fragment of the membrane and adopts a small angle with respect to the surface normal.
In conclusion, the addition of valinomycin and potassium to the mitochondrial suspension will decrease the proton motive force, but it will not drop to zero due to the remaining pH gradient component.
- This is supported by studies on the effects of valinomycin on mitochondrial function and the mechanism of ion transport across model lipid bilayer membranes 1, 2.
- The proton motive force is a critical component of mitochondrial function, and its decrease can have significant effects on cellular energy production and overall health.