Iron–Sulfur Models of Protein Active Sites

Iron–sulfur clusters appear in a great many proteins as both electron-transport and enzymatic sites (see Iron–Sulfur Proteins); for this reason there has been great interest for 30 years in the development and understanding of iron–sulfur model complexes. Both structure and properties of synthetic analogs of 1-, 2-, 3-, and 4-iron protein active sites have been studied extensively.1 This article will address the structural and chemical properties, synthesis, and catalytic activity of these synthetic analogs, as compared to the native protein-bound iron–sulfur cores. In general, iron–sulfur clusters are coordinated to native proteins via cysteine thiolate bonding, often in a Cys-X-Y-Cys motif (X, Y = nonsulfur containing amino acids). In clusters with more than one iron atom, μ2or μ3-sulfur linkages connect the iron atoms within the cluster. At the active site of proteins, iron–sulfur clusters perform a variety of functions, including electron transport and enzymatic activity. 2 RUBREDOXIN MODEL COMPLEXES