title: A motif for quinone binding sites in respiratory and photosynthetic systems.
abstract: Many of the membrane-bound protein complexes of respiratory and photosynthetic systems are reactive with quinones. To date, no clear structural relationship between sites that bind quinone has been defined, apart from that in the homologous family of "type II" photosynthetic reaction centres. We show here that a structural element containing a weak sequence motif is common to the Q(A) and Q(B) sites of bacterial reaction centres and the Q(i) site of the mitochondrial bc(1) complex. Analyses of sequence databases indicate that this element may also be present in the PsaA/B subunits of photosystem I, in the ND4 and ND5 subunits of complex I and, possibly, in the mitochondrial alternative quinol oxidase. This represents a first step in the structural classification of quinone binding sites.
authors.affiliation: Department of Biology, University College London, Glynn Laboratory of Bioenergetics, Gower Street, London, WC1E 6BT, UK.
authors.forename: N
authors.initials: N
authors.lastname: Fisher
authors.forename: P R
authors.initials: PR
authors.lastname: Rich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism*; D001665:Binding Sites; D002696:Chlamydomonas / Q000737:chemistry; D019414:Chlorobi / Q000737:chemistry; D014450:Electron Transport Complex III / Q000378:metabolism; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism; D045331:Photosystem I Protein Complex; D017434:Protein Structure, Tertiary; D016992:Rhodobacter / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D010837:Vitamin K 1 / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; C004532:quinone; D010837:Vitamin K 1; D014450:Electron Transport Complex III