Rieske protein



The iron-sulfur protein (ISP) component of cytochrome bc1 complex was first discovered and isolated by John S. Rieske and co-workers in 1964. The homologues of the Rieske proteins include ISP components of cytochrome b6f complex), aromatic-ring-hydroxylating dioxygenases (phthalate dioxygenase, benzene, napthalene and toluene 1,2-dioxygenases) and arsenite oxidase (EC 1.20.98.1). Comparison of amino acid sequences has revealed the following consensus sequence:


 * Cys-Xaa-His-(Xaa)15–17-Cys-Xaa-Xaa-His

The crystal structures of a number of Rieske proteins are known. The overall fold, comprising two subdomains, is dominated by antiparallel β-structure and contains the only α-helix. The smaller "cluster-binding" subdomains in mitochondrial and chloroplast proteins are virtually identical, whereas the large subdomains are substantially different in spite of a common folding topology. The [Fe2S2] cluster-binding subdomains have the topology of an incomplete antiparallel β-barrel. One iron atom of the Rieske [Fe2S2] cluster is coordinated by two cysteine residues and the other is coordinated by two histidine residues through the Nδ atoms. The ligands coordinating the cluster originate from two loops; each loop contributes one Cys and one His.