28] Overview of iron-sulfur proteins

Abstract

Publisher Summary This chapter provides an overview of iron–sulfur proteins. Iron–sulfur proteins are those in which iron is bound via sulfur-containing ligands. A diagram is depicted in the chapter to present a classification scheme for iron proteins that emphasizes the varieties of currently recognized Fe–S proteins. The groups of Fe–S proteins denoted “simple,” which contain no recognized prosthetic groups other than Fe–S clusters, appear to function mainly as electron carriers. Many of the simple Fe–S proteins are recognized as electron carriers, and for this property there are three relatively sensitive assay systems—namely, (1) the ferredoxin-dependent phosphoroclastic oxidation of pyruvate, catalyzed by ferredoxin-depleted extracts from Clostridium sp , (2) the ferredoxin-dependent reduction of NADP by illuminated heat-treated chloroplast preparations, and (3) the ferredoxin-dependent evolution of H 2 in the presence of sodium dithionite and hydrogenase. In addition to the number of iron atoms present in one of these centers, one needs to specify the oxidation state, which is generally indicated by the net charge state, computed on the assumption that the cysteines are formally present as mercaptide, the labile sulfur as sulfide, and the iron atoms as the formally ferric or ferrous state.