Cryogenic electron microscopy structures reveal how ATP and DNA binding in MutS coordinates sequential steps of DNA...

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• DNA mismatch repair (MMR) is crucial for genomic stability.
• The MutS protein initiates the MMR cascade by detecting DNA mismatches.
• Understanding MutS conformational dynamics during ATP hydrolysis is essential for MMR mechanism elucidation.

Purpose of the Study:

• To elucidate the mechanism by which ATP binding and hydrolysis induce conformational changes in Escherichia coli MutS.
• To investigate how DNA binding modulates the ATPase cycle of MutS.
• To reveal the structural basis for MutS conformational transitions during the MMR process.

Main Methods:

• Cryogenic electron microscopy (cryo-EM) was used to determine structures of E. coli MutS.
• Four structures captured sequential stages of the ATP hydrolysis cycle.
• Biophysical analyses were performed to study DNA binding and nucleotide interactions.

Main Results:

• Cryo-EM structures reveal ATP binding induces MutS dimer closing, while hydrolysis promotes opening.
• DNA binding prevents ATP hydrolysis during scanning and mismatch binding.
• DNA binding also inhibits ADP release in the sliding clamp state, with nucleotide release facilitated by single-stranded DNA.

Conclusions:

• ATP binding, hydrolysis, and DNA interaction collectively regulate MutS conformational states.
• These regulated conformational changes are critical for coordinating the sequential steps of DNA mismatch repair.
• The study provides structural insights into the dynamic mechanism of MutS in MMR.