Nonspecifically bound proteins spin while diffusing along DNA

Authors:
Open Access
Publisher website
Google Scholar
Abstract
Some proteins move along DNA, searching for a specific target. Now these proteins are shown to follow a helical path, i.e., they rotate while sliding, hence maintaining a specific orientation to the DNA helix. This is accomplished by tracking single molecules of labeled human oxoguanine DNA glycosylase 1, alone or bound to a bulky streptavidin moiety, and calculating their diffusion constants. It is known that DNA-binding proteins can slide along the DNA helix while searching for specific binding sites, but their path of motion remains obscure. Do these proteins undergo simple one-dimensional (1D) translational diffusion, or do they rotate to maintain a specific orientation with respect to the DNA helix? We measured 1D diffusion constants as a function of protein size while maintaining the DNA-protein interface. Using bootstrap analysis of single-molecule diffusion data, we compared the results to theoretical predictions for pure translational motion and rotation-coupled sliding along the DNA. The data indicate that DNA-binding proteins undergo rotation-coupled sliding along the DNA helix and can be described by a model of diffusion along the DNA helix on a rugged free-energy landscape. A similar analysis including the 1D diffusion constants of eight proteins of varying size shows that rotation-coupled sliding is a general phenomenon. The average free-energy barrier for sliding along the DNA was 1.1 ± 0.2 kBT. Such small barriers facilitate rapid search for binding sites.

This publication has 25 references indexed in Scilit: