title: Sequential processing of a mitochondrial tandem protein: insights into protein import in Schizosaccharomyces pombe.
abstract: The sequencing of the genome of Schizosaccharomyces pombe revealed the presence of a number of genes encoding tandem proteins, some of which are mitochondrial components. One of these proteins (pre-Rsm22-Cox11) consists of a fusion of Rsm22, a component of the mitochondrial ribosome, and Cox11, a factor required for copper insertion into cytochrome oxidase. Since in Saccharomyces cerevisiae, Cox11 is physically attached to the mitochondrial ribosome, it was suggested that the tandem organization of Rsm22-Cox11 is used to covalently tie the mitochondrial ribosome to Cox11 in S. pombe. We report here that pre-Rsm22-Cox11 is matured in two subsequent processing events. First, the mitochondrial presequence is removed. At a later stage of the import process, the Rsm22 and Cox11 domains are separated by cleavage of the mitochondrial processing peptidase at an internal processing site. In vivo data obtained using a tagged version of pre-Rsm22-Cox11 confirmed the proteolytic separation of Cox11 from the Rsm22 domain. Hence, the tandem organization of pre-Rsm22-Cox11 does not give rise to a persistent fusion protein but rather might be used to increase the import efficiency of Cox11 and/or to coordinate expression levels of Rsm22 and Cox11 in S. pombe.
authors.affiliation: Institut für Genetik, Technische Universität Dresden, Germany.
authors.forename: Oleh
authors.initials: O
authors.lastname: Khalimonchuk
authors.forename: Martin
authors.initials: M
authors.lastname: Ott
authors.forename: Soledad
authors.initials: S
authors.lastname: Funes
authors.forename: Kai
authors.initials: K
authors.lastname: Ostermann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rödel
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Herrmann
mesh_terms: D017398:Alternative Splicing; D015321:Gene Rearrangement; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism*; D008954:Models, Biological; D046188:Protein Modification, Translational; D021382:Protein Sorting Signals; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000378:metabolism*
chemical_list: C086106:COX11 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C502078:Rsm22 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins