Facilitated Target Location on DNA by IndividualEscherichia coli RNA Polymerase Molecules Observed with the Scanning Force Microscope Operating in Liquid

In Escherichia coli, transcription is carried out by a single enzyme, E. coli RNA polymerase (RNAP),1 and the rate of transcription initiation is controlled, in part, by the rate at which the polymerase can find the promoter. One problem that RNAP, and for that matter most other specific DNA-binding proteins, must solve is how to overcome the kinetic barrier of finding its specific binding site amid a large excess of nonspecific DNA. In 1968, Adam and Delbrück (1) proposed that the efficiency of a diffusion-controlled search could be enhanced by orders of magnitude if it were to take place in a space of lower dimensionality.