Iron—Sulfur Clusters in Enzymes: Themes and Variations

Abstract

Publisher Summary This chapter discusses the diversity of iron–sulfur proteins. From consideration of the primary and tertiary structure of the iron–sulfur proteins determined so far, it is possible to discern a number of distinct structural themes. Most of the complex proteins are constructed from domains, some of which are related to the ferredoxin-like sequences and Rieske iron–sulfur proteins. Differences are exhibited at several levels: (1) in the different types of iron–sulfur clusters, which have been identified by structure determination and by spectroscopy, (2) in the proteins that bind these clusters (the same type of cluster may be coordinated to protein domains of different sequences and structure), (3) in the other prosthetic groups that are present, and (4) in the different catalytic activities of the clusters. From studies of the ferredoxins and other small iron–sulfur proteins, it is known that there is a variety of iron–sulfur cluster types. These clusters are usually, but not invariably, coordinated to cysteine residues of the protein in conserved arrangements.