F-subunit reinforces torque generation in V-ATPase

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Vacuolar-type H(+)-pumping ATPases (V-ATPases) are crucial molecular motors involved in diverse cellular functions, including organelle pH regulation and ATP synthesis in bacteria.
• Each V-ATPase comprises a soluble catalytic domain (V1) and a membrane-embedded domain (Vo).
• The V1 domain contains the ATP-driven rotary unit, V[Formula: see text], composed of A, B, D, and F subunits, with the DF subcomplex acting as the rotary shaft.

Purpose of the Study:

• To investigate the specific role of the globular-shaped F-subunit in the rotary torque generation of the V[Formula: see text] motor.
• To determine the impact of the F-subunit's absence on the minimal ATP-driven rotary unit (A3B3D).

Main Methods:

• Utilized single-molecule techniques to observe the motion of V-ATPase rotary motors.
• Applied the fluctuation theorem to analyze motion trajectories and quantify torque generation.
• Compared torque generation in wild-type V1, A3B3D (lacking F-subunit), and a mutant with F-subunit fused to D-subunit.

Main Results:

• The A3B3D complex, lacking the F-subunit, exhibited approximately half the rotary torque of the wild-type V1 motor.
• Restoration of torque to wild-type levels was observed in a mutant V1 where the F-subunit was genetically fused to the D-subunit.
• These findings indicate that the F-subunit plays a significant role in reinforcing torque generation.

Conclusions:

• The globular-shaped F-subunit is essential for optimal torque generation in V-ATPases.
• The F-subunit likely acts to stabilize or enhance the mechanical output of the V[Formula: see text] rotary motor.
• Understanding the F-subunit's function provides insights into the mechanics of rotary molecular motors.