A novel Mre11 protein from the hyperthermophilic euryarchaeon Thermococcus barophilus Ch5 possesses 5'-3' exonuclease...

Area of Science:

• Biochemistry
• Molecular Biology
• Extremophile Research

Background:

• Mre11 proteins are essential for DNA repair and recombination, processing DNA ends to facilitate these processes.
• Characterizing Mre11 from hyperthermophilic archaea provides insights into enzyme function under extreme conditions.

Purpose of the Study:

• To biochemically characterize the Mre11 protein from Thermococcus barophilus Ch5 (Tba-Mre11).
• To investigate the roles of four conserved residues in Tba-Mre11's enzymatic activity and DNA binding.

Main Methods:

• Biochemical assays to determine exonuclease and endonuclease activities.
• Site-directed mutagenesis to create mutant Tba-Mre11 proteins.
• Analysis of DNA degradation and binding capabilities of wild-type and mutant proteins.

Main Results:

• Tba-Mre11 exhibits unique 5'-3' exonuclease activity on ssDNA and dsDNA, alongside endonuclease activity.
• Optimal activity was observed at 80°C and pH 7.5-9.5 with Mn2+.
• Residues D10, D51, and N86 are critical for DNA degradation, while D44 is essential for DNA binding but not degradation.

Conclusions:

• Tba-Mre11 possesses distinct enzymatic properties compared to other Mre11 homologs.
• Specific residues play differential roles in DNA processing and binding, highlighting functional divergence.
• This study provides the first characterization of Mre11 from the Thermococcus genus.