Structural and functional studies of MutS2 from Deinococcus radiodurans.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• MutS2 homologues are vital in prokaryotes for DNA repair and detoxification.
• The small mutS-related (Smr) domain is crucial for MutS2's endonucleolytic function, but its catalytic mechanism remains elusive.
• Deinococcus radiodurans possesses exceptional DNA repair capabilities, making it an ideal model for studying DNA repair mechanisms.

Purpose of the Study:

• To investigate the in vivo function of drMutS2 in Deinococcus radiodurans.
• To elucidate the catalytic mechanism and identify key residues of the drMutS2 Smr domain.
• To understand the role of drMutS2 in RecA-independent DNA repair pathways.

Main Methods:

• Construction of mutS2 and recA mutS2 double knockout mutants in Deinococcus radiodurans.
• Assessment of cellular sensitivity to ionizing radiation and oxidative agents.
• Crystallization of the drMutS2 Smr domain and manganese ion soaking for structural analysis.
• Site-directed mutagenesis to identify catalytic residues.

Main Results:

• The absence of drMutS2 increased sensitivity to radiation and oxidative stress, indicating a RecA-independent repair role.
• Mutagenesis identified glutamic acid 710 as a critical catalytic residue, essential for nuclease activity.
• High-resolution crystal structures (1.2 Å) of the manganese-derivative Smr domain revealed conformational changes in key acidic residues.

Conclusions:

• drMutS2 plays a significant role in RecA-independent DNA repair and oxidative stress resistance in Deinococcus radiodurans.
• Glutamic acid 710 is a crucial catalytic residue in the drMutS2 Smr domain, directly involved in its nuclease activity.
• Structural insights into the Smr domain provide a foundation for understanding the detailed catalytic mechanism of MutS2 proteins.