1: Nature  1997 Mar 20;386(6622):299-302 

Comment in:
 Nature. 1997 Mar 20;386(6622):217-9.

Direct observation of the rotation of F1-ATPase.

Noji H, Yasuda R, Yoshida M, Kinosita K Jr.

Research Laboratory of Resources Utilization, Tokyo Institute of Technology,
Yokohama, Japan.

Cells employ a variety of linear motors, such as myosin, kinesin and RNA
polymerase, which move along and exert force on a filamentous structure. But
only one rotary motor has been investigated in detail, the bacterial flagellum
(a complex of about 100 protein molecules). We now show that a single molecule
of F1-ATPase acts as a rotary motor, the smallest known, by direct observation
of its motion. A central rotor of radius approximately 1 nm, formed by its
gamma-subunit, turns in a stator barrel of radius approximately 5nm formed by
three alpha- and three beta-subunits. F1-ATPase, together with the
membrane-embedded proton-conducting unit F0, forms the H+-ATP synthase that
reversibly couples transmembrane proton flow to ATP synthesis/hydrolysis in
respiring and photosynthetic cells. It has been suggested that the gamma-subunit
of F1-ATPase rotates within the alphabeta-hexamer, a conjecture supported by
structural, biochemical and spectroscopic studies. We attached a fluorescent
actin filament to the gamma-subunit as a marker, which enabled us to observe
this motion directly. In the presence of ATP, the filament rotated for more than
100 revolutions in an anticlockwise direction when viewed from the 'membrane'
side. The rotary torque produced reached more than 40 pN nm(-1) under high load.

PMID: 9069291 [PubMed - indexed for MEDLINE]