Physical characterization of a totally synthetic rubredoxin

The entire polypeptide of hyperthermophilic Pyrococcus furiosus rubredoxin was synthesized in order to specifically probe structural determinants of protein thermostability. The uv-visible, circular dichroic, electron paramagnetic, and nuclear magnetic resonance spectra, and electrochemical properties, of the native and synthetic proteins were essentially identical. The synthetic protein had a half-life for denaturation of 24 hr at 80 degrees C. The synthetic protein is considerably more thermostable than nonhyperthermophilic rubredoxins, but not as stable as the native protein. Based on the spectroscopic evidence, it appears that the synthetic protein is incorporating iron properly to form holoprotein, but the peptide still may not be folded correctly.