Subunit rotation in Escherichia coli FoF1-ATP synthase during oxidative phosphorylation

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Respiration

Background:

• FoF1-ATP synthase is a crucial enzyme complex responsible for cellular energy production via oxidative phosphorylation.
• Understanding the mechanism of proton-driven subunit rotation is vital for elucidating energy transduction in biological systems.

Purpose of the Study:

• To provide direct evidence for proton-driven subunit rotation within the membrane-bound FoF1-ATP synthase complex.
• To investigate the role of proton transport and substrate availability (ADP and Pi) in this rotational mechanism.

Main Methods:

• Utilized a specifically engineered hybrid F1 sector with crosslinked beta and gamma subunits, and epitope-tagged beta subunits.
• Performed crosslinking/re-oxidation experiments after exposing the enzyme to ATP synthesis conditions.
• Investigated the effect of inhibiting proton transport through Fo and omitting ADP/Pi on subunit reorientation.

Main Results:

• Demonstrated significant reorientation of the epitope-tagged beta subunits into the crosslinked gamma position after ATP synthesis conditions.
• Confirmed that this subunit reorientation is dependent on proton transport through the Fo sector.
• Observed inhibition of rotation when proton flow was blocked or when ADP and Pi were absent.

Conclusions:

• Established that proton transport through Fo drives the rotation of the gamma subunit relative to the beta subunits in FoF1-ATP synthase.
• FoF1-ATP synthase represents a second known biological system where proton transport is directly coupled to mechanical subunit rotation.
• Provides mechanistic insight into the energy conversion process during oxidative phosphorylation.