Biochemical characterization of the nuclease stonura from the hyperthermophilic archaeon sulfolobus tokodaii

Abstract

The DNA nuclease gene ST2109 has been cloned from the hyperthermophilic archaeon Sulfolobus tokodaii and expressed in Escherichia coli. The recombinant protein StoNurA has been purified to homogeneity by affinity chromatography and gel filtration chromatography. Biochemical analyses demonstrated that StoNurA exhibited DNA binding and 5’–3’ exonuclease activities towards ssDNA and dsDNA. The temperature and pH optima of StoNurA were determined to be 65 °C and 8.0, respectively. The activity of StoNurA was found to be dependent of Mn2+, and its half-life of heat inactivation at 100 °C was 5 min. Gel filtration chromatography revealed that StoNurA could form dimers in solution. Pull-down assays also showed that StoNurA physically interacted with a DNA helicase (StoHerA). Our data suggest that NurA may play a key functional role in the processing of DNA recombinational repair.