We present here a movie of a typical transcription
run by a single RNA polymerase enzyme as described in the article "Single
molecule study of transcription and arrest by E. coli RNA polymerase"
by R. John Davenport, Gijs
J. L. Wuite, Robert Landick, and Carlos
Science (2000) V287:2497-2500.
The setup of the single molecule transcription
experiment is depicted above. The DNA (~10 kbp) and the RNA polymerase
are biotinylated (red crosses) allowing the stalled complexes to be attached
between the 2.2 µm streptavidin-coated beads (purple). After the
NTPs arrive in the fluid chamber the RNA polymerase transcribes the DNA,
resulting in a shortening of the tether between the beads. This decrease
in bead separation can be measured and directly observed as is shown in
Description of the movie
Approximately one frame every 5 seconds was selected to
speed up the movement of the transcription process. A total of ~10 minutes
of transcription is displayed and the movie is "looped" 8 times. When a
new loop starts the total shortening of the DNA tether is clearly visible.
6:09:00:23 Start of loop; NTPs arrive in chamber together with beads in solution
6:09:25:25 Bead from solution captured in laser trap
6:10:25:14 Bead-center-to-bead-center distance measured in microns
6:10:25:14 - 6:18:41:03 Shortening of the tether due to transcription clearly visible
6:18:41:03 End of loop
0.5M RealPlayer Movie