title: Pentatricopeptide repeat proteins in Trypanosoma brucei function in mitochondrial ribosomes.
abstract: The pentatricopeptide repeat (PPR), a degenerate 35-amino-acid motif, defines a novel eukaryotic protein family. Plants have 400 to 500 distinct PPR proteins, whereas other eukaryotes generally have fewer than 5. The few PPR proteins that have been studied have roles in organellar gene expression, probably via direct interaction with RNA. Here we show that the parasitic protozoan Trypanosoma brucei encodes 28 distinct PPR proteins, an extraordinarily high number for a nonplant organism. A comparative analysis shows that seven out of eight selected PPR proteins are mitochondrially localized and essential for oxidative phosphorylation. Six of these are required for the stabilization of mitochondrial rRNAs and, like ribosomes, are associated with the mitochondrial membranes. Furthermore, one of the PPR proteins copurifies with the large subunit rRNA. Finally, ablation of all of the PPR proteins that were tested induces degradation of the other PPR proteins, indicating that they function in concert. Our results show that a significant number of trypanosomal PPR proteins are individually essential for the maintenance and/or biogenesis of mitochondrial rRNAs.
authors.affiliation: Department of Biology/Cell and Developmental Biology, University of Fribourg, Chemin du Musée 10, CH-1700, Fribourg, Switzerland.
authors.forename: Mascha
authors.initials: M
authors.lastname: Pusnik
authors.forename: Ian
authors.initials: I
authors.lastname: Small
authors.forename: Laurie K
authors.initials: LK
authors.lastname: Read
authors.forename: Thomas
authors.initials: T
authors.lastname: Fabbro
authors.forename: André
authors.initials: A
authors.lastname: Schneider
mesh_terms: D000818:Animals; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010085:Oxidative Phosphorylation; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012335:RNA, Ribosomal / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D012270:Ribosomes / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism
chemical_list: D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D012335:RNA, Ribosomal