Figure 6.

Influence of protein concentration on target searches. (A) Facilitated diffusion will be favored at low protein concentrations because the initial encounter with the DNA will most often occur at non-specific sites. The protein can then diffuse along the DNA to its target site. (B) Higher protein concentrations favor 3D searches because the relative increase in protein abundance increases the probability of a direct collision with the target site. Facilitated diffusion related processes such as sliding/hopping can still occur at high protein concentrations, but those proteins undergoing such processes are less likely to reach the target site before those that collide directly with the target. An educational video illustrating these concepts can be found at: <http://www.youtube.com/watch?v=tIWv7rAe44M>.