The delta-subunit of pyruvate ferredoxin oxidoreductase from Pyrococcus furiosus is a redox-active, iron-sulfur protein: evidence for an ancestral relationship with 8Fe-type ferredoxins.

Pyruvate ferredoxin oxidoreductase (POR) from the hyperthermophilic archaeon Pyrococcus furiosus (Pf) catalyzes the final oxidative step in carbohydrate fermentation in which pyruvate is oxidized to acetyl-CoA and CO2, coupled to the reduction of ferredoxin (Fd). POR is composed of two ‘catalytic units' of molecular mass ∼120 kDa. Each unit consists of four subunits, αβγδ, with masses of approximately 44, 36, 20, and 12 kDa, respectively, and contains at least two [4Fe-4S] clusters. The precise mechanism of catalysis and the role of the individual subunits are not known. The gene encoding the δ-subunit of Pf POR has been expressed in E. coli, and the protein was purified after reconstitution with iron and sulfide. The reconstituted δ-subunit (recPOR-δ) is monomeric with a mass of 11 879 ± 1.2 Da as determined by mass spectrometry, in agreement with that predicted from the gene sequence. Purified recPOR-δ contains 8 Fe mol/mol and remained intact when incubated at 85 °C for 2 h, as judged by its visible ab...