WFU Physics Colloquium

TITLE: Conformational dynamics that allow proteins to detect DNA mismatches and signal for repair

SPEAKER: Professor Keith Weninger,

TIME: Wednesday March 6, 2013 at 4:00 PM

PLACE: Room 101 Olin Physical Laboratory

The DNA mismatch repair system is critical for accurate DNA replication. This system is highly conserved across organisms ranging from bacteria to humans reflecting the importance of minimizing genomic defects during cell division. The mismatch repair protein MutS has been identified the key factor that detects single DNA base mismatches and signals for their repair. A temporally resolved understanding of the molecular details of the MutS:DNA interactions during mismatch repair initiation has been difficult to obtain because these transient interactions occur within an overwhelming background of properly matched DNA basepairs.

We used single molecule fluorescence resonance energy transfer (smFRET) to characterize conformational changes in MutS as it scans homoduplex DNA, recognizes DNA mismatches, activates to a sliding clamp, and interacts with downstream proteins in the repair signaling pathway. We found a series of sequential conformational changes that provide a mechanistic picture of: i) DNA bending , ii) conformational changes within MutS, iii) motion of MutS scanning along DNA, iv) ATP binding that commits MutS:mismatch DNA complexes to signaling states, and v) the modulation of these MutS behaviors by other regulatory factors.