A PROTEIN DISULFIDE OXIDOREDUCTASE FROM THE ARCHAEON PYROCOCCUS-FURIOSUS CONTAINS 2 THIOREDOXIN FOLD UNITS

Protein disulfide bond formation is a rate limiting step in protein fo lding and is catalyzed by enzymes belonging to the protein disulfide o xidoreductase superfamily, including protein disulfide isomerase (PDI) in eucarya and DsbA in bacteria, The first high resolution X-ray crys tal structure of a protein disulfide oxidoreductase from the hyperther mophilic archaeon Pyrococcus furiosus reveals structural details that suggest a relation to eukaryotic PDI. The protein consists of two homo logous structural units with low sequence identity. Each unit contains a thioredoxin fold with a distinct CXXC active site motif. The access ibilities of both active sites are rather different as are, very likel y, their redox properties. The protein shows the ability to catalyze t he oxidation of dithiols as well as the reduction of disulfide bridges .