Improving the thermostability and stress tolerance of an archaeon hyperthermophilic superoxide dismutase by fusion with a unique N-terminal domain.

The superoxide dismutase from the archaeon Sulfolobus solfataricus (SOD Ss ) is a well-studied hyperthermophilic SOD with crystal structure and possible thermostability factors characterized. Previously, we discovered an N-terminal domain (NTD) in a thermophilic SOD from Geobacillus thermodenitrificans NG80-2 which confers heat resistance on homologous mesophilic SODs. The present study therefore aimed to further improve the thermostability and stress tolerance of SOD Ss via fusion with this NTD. The recombinant protein, rSOD Ss , exhibited improved thermophilicity, higher working temperature, improved thermostability, broader pH stability, and enhanced tolerance to inhibitors and organic media than SOD Ss without any alterations in its oligomerization state. These results suggest that the NTD is an excellent candidate for improving stability of both mesophilic and thermophilic SOD from either bacteria or archaea via simple genetic manipulation. Therefore, this study provides a general, feasible and highly useful strategy for generating extremely thermostable SODs for industrial applications.