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ATP synthase - the rotary engine in the cell
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ATP synthase
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ATP is called the general energy coin in the cell.
One person produces and consumes his or her body weight in ATP in a day.
Such rapid turnover of ATP is supported by
the efficient production of ATP in mitochondria, a micro organ
in the cell. A gigantic enzyme called ATP synthase whose
molecular weight is over 500 kDa, synthesizes ATP in the mitochondria.
Very similar enzymes are working in plant chloroplasts and
bacterial cell membranes. We have been studying the ATP synthase
from a thermophilic bacterium which was isolated from a Japanese
hot spring and from thylakoid membranes of plant chloroplasts.
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ATP synthase is a rotary motor
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In his Binding Change hypothesis, Paul Boyer had predicted that
some subunits in the ATP synthase rotated during catalysis.
In 1997, we succeeded in visualization of the rotation of
the gamma subunit in the central cavity of the surrounding alpha3-beta3
hexagon, using fluorescently labeled actin filaments.
We videotaped the rotation of the single molecules and gave
final evidence for Boyer’s hypothesis. Our results had
a great influence on the Nobel Prize selection for Drs.
Walker and Boyer (Nature 389. 771, 1997). Now, single molecule
experiments have opened a new area of single-molecule bioenergetics.
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Rotation of the gamma subunit of thermophilic F1-ATPas was
observed directly with an epifluorescent microscope.
The enzyme was immobilized on a coverslip through His-tag
introduced at the N-termini of the beta subunit.
Fluorescently labeled actin filament was attached to the gammma subunit for the observation.
Images of the rotating particles were taken with a CCD camera attached to an image
intensifier, recorded on an 8-mm video tape and now can be viewed
by just clicking on the figures below.
(Noji et al. Nature 386 299-302 1997)
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Online animation and the movie is available in the site of CRL, Tokyo Tech as well.
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