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Updated: May 8, 2026
Application of Stopped-flow Kinetics Methods to Investigate the Mechanism of Action of a DNA Repair Protein
Published on: March 31, 2010
Slow conformational changes in MutS and DNA direct ordered transitions between mismatch search, recognition and
Anushi Sharma1, Christopher Doucette, F Noah Biro
1Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459, USA.
Abstract:
MutS functions in mismatch repair (MMR) to scan DNA for errors, identify a target site and trigger subsequent events in the pathway leading to error removal and DNA re-synthesis. These actions, enabled by the ATPase activity of MutS, are now beginning to be analyzed from the perspective of the protein itself. This study provides the first ensemble transient kinetic data on MutS conformational dynamics as it works with DNA and ATP in MMR. Using a combination of fluorescence probes (on Thermus aquaticus MutS and DNA) and signals (intensity, anisotropy and resonance energy transfer), we have monitored the timing of key conformational changes in MutS that are coupled to mismatch binding and recognition, ATP binding and hydrolysis, as well as sliding clamp formation and signaling of repair. Significant findings include (a) a slow step that follows weak initial interaction between MutS and DNA, in which concerted conformational changes in both macromolecules control mismatch recognition, and (b) rapid, binary switching of MutS conformations that is concerted with ATP binding and hydrolysis and (c) is stalled after mismatch recognition to control formation of the ATP-bound MutS sliding clamp. These rate-limiting pre- and post-mismatch recognition events outline the mechanism of action of MutS on DNA during initiation of MMR.
Insights
MutS protein dynamics in DNA mismatch repair (MMR) were studied using fluorescence. Key conformational changes linked to DNA/ATP binding and hydrolysis control error recognition and repair initiation.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- MutS is crucial for DNA mismatch repair (MMR), scanning DNA for errors.
- Its ATPase activity drives DNA repair processes.
- Understanding MutS conformational dynamics is key to elucidating MMR mechanisms.
Purpose of the Study:
- To provide the first ensemble transient kinetic data on MutS conformational dynamics during MMR.
- To analyze MutS interactions with DNA and ATP.
- To reveal the timing of conformational changes in MutS during the MMR pathway.
Main Methods:
- Utilized fluorescence probes on Thermus aquaticus MutS and DNA.
- Monitored signals including intensity, anisotropy, and resonance energy transfer.
- Applied ensemble transient kinetic analysis.
Main Results:
- Identified a slow step after initial MutS-DNA interaction, involving concerted conformational changes for mismatch recognition.
- Observed rapid, binary switching of MutS conformations coupled to ATP binding and hydrolysis.
- Found that conformational switching is stalled post-mismatch recognition, controlling ATP-bound MutS sliding clamp formation.
Conclusions:
- Rate-limiting conformational changes before and after mismatch recognition dictate MutS function in initiating MMR.
- MutS conformational dynamics are tightly regulated by DNA and ATP interactions.
- This study provides a mechanistic framework for MutS action in DNA repair initiation.
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