MutS-mediated detection of DNA mismatches using atomic force microscopy

We have developed an atomic force microscopy-based method for detecting DNA base-pair mismatches using MutS protein isolated from E. coli. MutS is a biological sensor and a locator of DNA base-pair mismatches. It binds specifically to a mismatched DNA base pair and initiates a process of DNA repair. To test the possibility of visually detecting mismatched base pairs by atomic force microscopy, we prepared DNA templates ~500 bp in length consisting of a single or multiple base-pair mismatches. We demonstrate that MutS binding sites on individual DNA molecules were readily detectable by atomic force microscopy and that the observed positions were in good agreement with the predicted sites of base-pairs mismatches at a few-nanometer resolution. The technique described here is rapid and sensitive and is expected to be useful in screening mutations and DNA polymorphisms.