Flow-force relationships during energy transfer between mitochondrial proton pumps

Area of Science:

• Mitochondrial bioenergetics
• Proton pump function
• Energy transduction

Background:

• Investigating proton pumps in submitochondrial particles is crucial for understanding cellular energy production.
• The relationship between proton motive force and pump activity is complex and influenced by various factors.

Purpose of the Study:

• To investigate the effect of inhibitors, uncouplers, and ions on proton pump activity.
• To explore the relationship between input force (delta mu H+), and output flows of ATPase, redox, and transhydrogenase proton pumps.

Main Methods:

• Studied the impact of inhibitors (oligomycin, malonate), uncouplers, and permeant ions (ClO4-) on proton pumps.
• Measured output flows of ATPase, redox, and transhydrogenase H(+)-pumps in submitochondrial particles.
• Analyzed the relationship between input force (delta mu H+) and proton pump output flows under various conditions.

Main Results:

• Transhydrogenase proton pump flow linearly correlates with delta mu H+ across a wide range, irrespective of the generating pump or inhibitors used.
• ATPase and site I redox proton pumps show steep dependence on delta mu H+; flow-force relationships vary with the method of delta mu H+ depression.
• Malonate inhibits ATPase more than uncouplers, which are more inhibitory than lipophilic anions; oligomycin inhibits redox pumps more than uncouplers, which are more inhibitory than ClO4-.

Conclusions:

• Transhydrogenase proton pump exhibits a distinct, linear flow-force relationship compared to other pumps.
• Results support a delocalized interaction model for transhydrogenase with other mitochondrial proton pumps.
• Differential inhibition patterns highlight unique regulatory mechanisms of different proton pumps.