F-subunit reinforces torque generation in V-ATPase

Jun Ichi Kishikawa, Akihiko Seino, Atsuko Nakanishi, Naciye Esma Tirtom, Hiroyuki Noji, Ken Yokoyama, Kumiko Hayashi

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Vacuolar-type H+-pumping ATPases (V-ATPases) perform remarkably diverse functions in eukaryotic organisms. They are present in the membranes of many organelles and regulate the pH of several intracellular compartments. A family of V-ATPases is also present in the plasma membranes of some bacteria. Such V-ATPases function as ATP-synthases. Each V-ATPase is composed of a water-soluble domain (V1) and a membrane-embedded domain (V o). The ATP-driven rotary unit, V 1, is composed of A, B, D, and F subunits. The rotary shaft (the DF subcomplex) rotates in the central cavity of the A3B3-ring (the catalytic hexamer ring). The D-subunit, which has a coiled-coil domain, penetrates into the ring, while the F-subunit is a globular-shaped domain protruding from the ring. The minimal ATP-driven rotary unit of V1 is comprised of the A3B 3D subunits, and we therefore investigated how the absence of the globular-shaped F-subunit affects the rotary torque generation of V1. Using a single-molecule technique, we observed the motion of the rotary motors. To obtain the torque values, we then analyzed the measured motion trajectories based on the fluctuation theorem, which states that the law of entropy production in non-equilibrium conditions and has been suggested as a novel and effective method for measuring torque. The measured torque of A 3B3D was half that of the wild-type V1, and full torque was recovered in the mutant V1, in which the F-subunit was genetically fused with the D-subunit, indicating that the globular-shaped F-subunit reinforces torque generation in V1.

Original languageEnglish
Pages (from-to)415-422
Number of pages8
JournalEuropean Biophysics Journal
Issue number8-9
Publication statusPublished - 2014 Sept


  • F-subunit
  • Fluctuation theorem
  • Torque generation

ASJC Scopus subject areas

  • Biophysics


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