1rie: Difference between revisions

BACKGROUND: The 'Rieske' iron-sulfur protein is the primary electron, acceptor during hydroquinone oxidation in cytochrome bc complexes. The, spectroscopic and electrochemical properties of the 'Rieske' [2Fe-2S], cluster differ significantly from those of other iron-sulfur clusters. A, 129-residue water soluble fragment containing the intact [2Fe-2S] cluster, was isolated following proteolytic digestion of the bc1 complex and used, for structural studies. RESULTS: The structure of the Rieske iron-sulfur, fragment containing the reduced [2Fe-2S] cluster has been determined using, the multiwavelength anomalous diffraction (MAD) technique and refined at, 1.5 A resolution. The fragment has a novel overall fold that includes, three sheets of beta strands. The iron atoms of the [2Fe-2S] cluster are, coordinated by two cysteine (Fe-1) and two histidine (Fe-2) residues, respectively, with the histidine ligands completely exposed to the, solvent. This is in contrast to the four cysteine coordination pattern, observed in previously characterised [2Fe-2S] ferredoxins. The, cluster-binding fold is formed by two loops connected by a disulfide, bridge; these loops superpose with the metal-binding loops of rubredoxins., The environment of the cluster is stabilised by an extensive hydrogen-bond, network. CONCLUSIONS: The high-resolution structure supports the proposed, coordination pattern involving histidine ligands and provides a basis for, a detailed analysis of the spectroscopic and electrochemical properties., As the cluster is located at the tip of the protein, it might come into, close contact with cytochrome b. The exposed N epsilon atoms of the, histidine ligands of the cluster are readily accessible to quinones and, inhibitors within the hydroquinone oxidation (QP) pocket of the bc1, complex and may undergo redox-dependent protonation/deprotonation.

1RIE is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with FES as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Ubiquinol--cytochrome-c_reductase Ubiquinol--cytochrome-c reductase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.10.2.2 1.10.2.2] Structure known Active Site: IRO. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1RIE OCA].  

''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov  5 14:59:33 2007''