Dynamic interactions of the tumor suppressor protein p53 with a DNA fragment containing a p53-specific consensus sequence were directly observed on a single-molecule basis by time-lapse tapping mode atomic force microscopy (AFM) in liquid. Divalent cations were used to loosely attach both DNA and p53 to a mica surface so they could be imaged by time-lapse AFM while being sufficiently mobile to interact with each other. Various interactions of p53 with DNA were imaged in real-time, including dissociation/re-association, sliding and possibly direct binding to the specific sequence. Two modes of target recognition of p53 were detected: (a) direct binding, and (b) initial nonspecific binding with subsequent translocation by one-dimensional diffusion of the protein along the DNA to the specific site. These results give new insights to the motion of single biomolecules.
Tilman E. Schaffer
Molecular Biology Dept., Max Planck Institute for Biophys. Chemistry
Am Fassberg 11, Goettingen 37077 GERMANY
Phone: +49 551 201-1762
Fax: +49 551 201-1467