Ubiquinol-cytochrome c reductase, iron-sulphur subunit <p>These sequences represent the Proteobacterial and mitochondrial type of the Rieske [2Fe-2S] iron-sulphur subunit as found in ubiquinol-cytochrome c reductase. Not included in this group are the Rieske iron-sulphur protein as found in the cytochrome b6-f complex of the Cyanobacteria and chloroplasts. Most members of this family have a recognizable twin-arginine translocation (tat) signal sequence (DeltaPh-dependent translocation in chloroplast) for transport across the membrane with the 2Fe-2S group already bound. These signal sequences include a motif resembling RRxFLK before the transmembrane helix. </p>