Spectroscopic evidence for site specific chemistry at a unique iron site of the [4Fe-4S] cluster in ferredoxin:Thioredoxin reductase

Abstract

Ferredoxin:thioredoxin reductase (FTR) catalyzes the reduction of the disulfide in thioredoxin in two one-electron steps using an active site comprising a [4Fe-4S] in close proximity to a redox active disulfide. Mössbauer spectroscopy has been used to investigate the ligation and electronic properties of the [4Fe-4S] cluster in as-prepared FTR which has the active-site disulfide intact and in the N-ethylmaleimide (NEM)-modified form which provides a stable analogue of the one-electron-reduced heterodisulfide intermediate and has one of the cysteines of the active-site disulfide alkylated with NEM. The results reveal novel site-specific cluster chemistry involving weak interaction of the acti..