PH-jump-induced ADP phosphorylation in mitochondria

Area of Science:

• Mitochondrial biology
• Bioenergetics
• Cellular respiration

Background:

• Mitochondria are crucial for cellular energy production through oxidative phosphorylation.
• Mitochondrial function can be impaired by factors such as aging and physical stress like freeze-thaw cycles.
• Uncoupling of oxidative phosphorylation disrupts the normal ATP synthesis pathway.

Purpose of the Study:

• To investigate the conditions under which uncoupled mitochondria can synthesize ATP.
• To determine the parameters of external pH changes that induce ATP synthesis.
• To characterize the mechanism of pH-jump-induced ATP synthesis.

Main Methods:

• Utilized isolated mitochondria subjected to aging or freeze-thaw treatments.
• Applied rapid changes in external pH (pH jumps) to mitochondrial suspensions.
• Measured ATP synthesis in response to pH gradients.
• Assessed the effect of oligomycin on pH-jump-induced ATP synthesis.

Main Results:

• Uncoupled mitochondria synthesized ATP following a rapid increase, but not a decrease, in external pH.
• Maximal ATP yield (approx. 2.5 ATP/electron-transport chain) was achieved when the pH jump exceeded 0.7 units and crossed the 8.1-8.3 range.
• Oligomycin completely inhibited this pH-jump-induced ATP synthesis, indicating reliance on ATP synthase.

Conclusions:

• Mitochondrial ATP synthesis can be driven by artificial proton gradients generated by rapid external pH increases.
• The efficiency of this process is dependent on the magnitude and trajectory of the pH change.
• The involvement of the F1F0-ATP synthase complex is confirmed by oligomycin inhibition.