1: FASEB J  1999 Dec;13 Suppl 2:S201-8 

Real time imaging of rotating molecular machines.

Kinosita K Jr.

Department of Physics, Faculty of Science and Technology, Keio University,
Yokohama, Japan. kazuhiko@phys.keio.ac.jp

Observation of true rotation has been relatively rare in living systems, but
there may be many molecular machines that rotate. Molecular rotations
accompanying function can be imaged in real time under an optical microscope by
attaching to the protein machine either a small tag such as a single fluorophore
or a tag that is huge compared with the size of the protein. As an example of
the former approach, axial rotation of an actin filament sliding over myosin has
been measured quantitatively by attaching a fluorophore rigidly to the filament
and imaging the orientation of the fluorophore continuously by polarization
microscopy. As a huge tag in the latter approach, an actin filament turned out
to be quite useful. Using this tag, the enzyme F1-ATPase has been shown to be a
rotary stepper motor made of a single molecule. Further, the efficiency of this
ATP-fueled motor has been shown to reach almost 100%. The two examples above
demonstrate that one can now image conformational changes, which necessarily
involve reorientation, in a single protein molecule during function.
Single-molecule physiology is no longer a dream.

Publication Types:
Review
Review, Tutorial

PMID: 10619128 [PubMed - indexed for MEDLINE]