1: Nature  2001 Apr 19;410(6831):898-904 

Comment in:
 Nature. 2001 Apr 19;410(6831):878-9, 881.

Resolution of distinct rotational substeps by submillisecond kinetic analysis of
F1-ATPase.

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

CREST 'Genetic Programming' Team 13, Teikyo University Biotechnology Center 3F,
Nogawa 907, Miyamae-Ku, Kawasaki 216-0001, Japan.

The enzyme F1-ATPase has been shown to be a rotary motor in which the central
gamma-subunit rotates inside the cylinder made of alpha3beta3 subunits. At low
ATP concentrations, the motor rotates in discrete 120 degrees steps, consistent
with sequential ATP hydrolysis on the three beta-subunits. The mechanism of
stepping is unknown. Here we show by high-speed imaging that the 120 degrees
step consists of roughly 90 degrees and 30 degrees substeps, each taking only a
fraction of a millisecond. ATP binding drives the 90 degrees substep, and the 30
degrees substep is probably driven by release of a hydrolysis product. The two
substeps are separated by two reactions of about 1 ms, which together occupy
most of the ATP hydrolysis cycle. This scheme probably applies to rotation at
full speed ( approximately 130 revolutions per second at saturating ATP) down to
occasional stepping at nanomolar ATP concentrations, and supports the
binding-change model for ATP synthesis by reverse rotation of F1-ATPase.

PMID: 11309608 [PubMed - indexed for MEDLINE]