Comparison of the binding sites of plant ferredoxin for two ferredoxin-dependent enzymes

Abstract

Differential chemical modification of acidic residues was used to map the binding site of plant ferredoxin (Fd) for the chloroplast enzyme ferredoxin:thioredoxin reductase (FTR). Binding of FTR to Fd inhibits chemical modification of Fd residues D34, D65, E92, E93, E94 and C-terminal A97. The binding site demarcated by these residues differs from that for ferredoxin:NADP + reductase (FNR). The FTR site includes C-terminal residues but not helix 24–31, which is part of the FNR site. Both sites enclose the [2Fe-2S] cluster.