Complex Unfolding Events of Sso 7d from S. solfataricus at High Temperature and High Pressure

摘要

We have studied the unfolding events of the archaebacterial Sso 7d and some of its mutant forms at high temperature and high pressure by a combination of UV absorbance spectroscopy in the 4~(th) derivative mode, ANS binding and molecular dynamics simulation. UV absorbance probed the changes in polarity of Tyr33, ANS binding (fluorescence increase) the exposure of the hydrophobic core to water, and the simulation helped to understand structural changes in the outer sphere protein segments. Our results suggest that unfolding is not a concerted process but affects different protein domains sequentially. The adaptation of the protein to high temperature appears to result from an increased flexibility of outer residues, whereas the hydrophobic core remains stable.