High hydrostatic pressure-induced conformational changes in protein disulfide oxidoreductase from the hyperthermophilic archaeon Pyrococcus furiosus. A Fourier-transform infrared spectroscopic study.

Protein disulfide oxidoreductases (PDOs) are ubiquitous redox enzymes that catalyse dithiol-disulfide exchange reactions. PDOs have been well studied in bacteria and eukarya, and they have been described in a number of thermophilic and hyperthermophilic species, where they play a critical role in the structural stabilization of intracellular proteins. In this study, the effect of high hydrostatic pressure on the structural properties of PDO from the hyperthermophilic archaeon Pyrococcus furiosus (PfPDO) was analysed in order to gain insights on the possible mechanisms used to endure extreme environmental conditions. The protein is highly thermostable and the data indicate that PfPDO is highly piezostable as well, and that different areas of the protein have a different local compressibility and resistance to high hydrostatic pressure. In particular, the results show that alpha-helices are more sensitive to pressure up to 5 kbar, whilst within 5-9 kbar the loss of beta-sheets is more pronounced than the loss of alpha-helices. Examination of the PfPDO structure and calculations of the solvent accessible surface areas for each amino acid indicate that 42% of the PfPDO residues are buried and that the protein contains four small internal hydrophobic cavities. These findings are discussed in terms of important factors contributing to the high piezostability and thermostability of the enzyme.