Large conformational changes in MutS during DNA scanning, mismatch recognition and repair signalling

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• The MutS protein is crucial for DNA mismatch repair, identifying and targeting mismatched DNA bases.
• Understanding the transient conformational states of MutS during repair signaling is limited.

Purpose of the Study:

• To investigate the conformational dynamics of the MutS protein during the DNA mismatch repair signaling process.
• To elucidate the role of nucleotide binding in MutS conformational changes and repair initiation.

Main Methods:

• Employed single-molecule fluorescence resonance energy transfer (smFRET) to monitor MutS conformational dynamics in real-time.
• Utilized steady-state measurements in the presence of nucleotides (ATP and ADP) to assess their impact on MutS conformation.

Main Results:

• Free and DNA-scanning MutS proteins exhibit dynamic interconversion among multiple conformations.
• Mismatch recognition induces a conformational lock in MutS, restricting it to a single state.
• Conversion to the repair-signaling sliding clamp form requires both ATP and ADP binding, proceeding through two sequential conformational changes.

Conclusions:

• The transition from mismatch recognition to the sliding clamp involves distinct intermediate conformations that persist for seconds.
• These stable intermediate states facilitate interactions with downstream repair proteins, enabling efficient DNA repair.
• This study provides critical insights into the dynamic conformational landscape of MutS during DNA mismatch repair signaling.