A single-point mutation in the extreme heat- and pressure-resistant Sso7d protein from Sulfolobus solfataricus leads to a major rearrangement of the hydrophobic core

The solution structure of the F31A mutant was determined using nuclear magnetic resonance spectroscopy. The most remarkable finding was the change in orientation of the Trp23 side chain, which in the wild type is completely exposed to the solvent. In the mutant, it remains largely buried in the aromatic cluster, preventing the formation of a cavity in the hydrophobic core. Other changes produced by the mutation of the heat- and pressure resistant Sso7d protein from Sulfolobus solfataricus were the distortion of the beta-sheets and increased flexibility in parts of the backbone.