Hyper-thermostability of CutA1 protein, with a denaturation temperature of nearly 150 °C

We found that the CutA1 protein, from Pyrococcus horikoshii (PhCutA1), has an extremely high denaturation temperature (Td) of nearly 150 °C, which exceeds the highest record determined by DSC by about 30 °C. To elucidate the mechanism of the ultra-high stability of PhCutA1, we analyzed the crystal structures of CutA1 proteins from three different sources, P. horikoshii, Thermus thermophilus, and Escherichia coli, with different growth temperatures (98, 75, and 37 °C). This analysis revealed that the remarkably increased number of ion pairs in the monomeric structure contributes to the stabilization of the trimeric structure and plays an important role in enhancing the Td, up to 150 °C, for PhCutA1.