title: From one gene to two proteins: the biogenesis of cytochromes b and c1 in Bradyrhizobium japonicum.
abstract: Genes coding for polyproteins that are cleaved posttranslationally into two or more functional proteins are rarely found in prokaryotes. One example concerns the biogenesis of the Bradyrhizobium japonicum cytochromes b and c1, two of the three constituent subunits of ubiquinol-cytochrome-c reductase (ubiquinol:ferricytochrome-c oxidoreductase, EC 1.10.2.2); the respective apoproteins for these subunits are encoded by the 5' and 3' halves of a single gene, fbcH. These two halves are linked by an extra piece of DNA encoding a characteristic signal peptide for protein translocation across the cytoplasmic membrane. Processing of the fbcH gene product is shown to occur at a typical signal peptidase recognition site. This reaction is reminiscent of that catalyzed by the regular bacterial signal peptidase that normally cleaves off presequences from the N termini of translocated proteins. Mutational alteration of the signal peptidase recognition site within FbcH results in the appearance of an uncleaved bc1 fusion protein in the membrane. Additionally, a functional heme-binding site in the apocytochrome c1 section of FbcH is shown to be a necessary prerequisite for the formation of the bc1 complex.
authors.affiliation: Mikrobiologisches Institut, Eidgenössische Technische Hochschule, ETH-Zentrum, Zürich, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Thöny-Meyer
authors.forename: P
authors.initials: P
authors.lastname: James
authors.forename: H
authors.initials: H
authors.lastname: Hennecke
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002876:Chromosomes, Bacterial; D003573:Cytochrome b Group / Q000235:genetics* / Q000378:metabolism; D003575:Cytochromes c1 / Q000235:genetics* / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006418:Heme / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D011499:Protein Processing, Post-Translational; D012230:Rhizobiaceae / Q000235:genetics* / Q000378:metabolism; D012697:Serine Endopeptidases
chemical_list: D003573:Cytochrome b Group; D008565:Membrane Proteins; D015345:Oligonucleotide Probes; D006418:Heme; D003575:Cytochromes c1; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase