Effects of the N-terminal and C-terminal domains of Meiothermus ruber CBS-01 trehalose synthase on thermostability and activity.

Numerous trehalose synthases (TreS) from thermophilic microorganisms have extra C-terminal domains. To determine the function of the N- and C-terminal domains of TreS from the thermophilic bacterium Meiothermus ruber CBS-01, the two domains were expressed. From the findings, the N-terminal domain from M. ruber was not active when compared with that from Thermus thermophilus, which had been studied previously. The circular dichroism spectrum showed that the secondary structure of N-terminal domain from M. ruber underwent a greater change than that of C terminus. In addition, the N-terminal domain from T. thermophilus and C terminus from M. ruber were fused. The fusion protein TSTtMr was more efficient and thermostable than the TreS from M. ruber. The N-terminal domain from M. ruber and C terminus from T. thermophilus were fused. The optimum temperature and thermostability of fusion protein TSMrTt were similar to the TreS from M. ruber. It was presumed that aside from the C-terminal domain, the N-terminal domain of TreS from thermophilic bacteria could influence thermostability. For the TreS from M. ruber, the mutant protein R392F led to a complete loss in activity, and R392A showed a sharp decrease in activity.