title: Biogenesis of a Mitochondrial Outer Membrane Protein inTrypanosoma brucei: TARGETING SIGNAL AND DEPENDENCE ON A UNIQUE BIOGENESIS FACTOR.
abstract: The mitochondrial outer membrane (OM) contains single and multiple membrane-spanning proteins that need to contain signals that ensure correct targeting and insertion into the OM. The biogenesis of such proteins has so far essentially only been studied in yeast and related organisms. Here we show that POMP10, an OM protein of the early diverging protozoanTrypanosoma brucei, is signal-anchored. Transgenic cells expressing variants of POMP10 fused to GFP demonstrate that the N-terminal membrane-spanning domain flanked by a few positively charged or neutral residues is both necessary and sufficient for mitochondrial targeting. Carbonate extraction experiments indicate that although the presence of neutral instead of positively charged residues did not interfere with POMP10 localization, it weakened its interaction with the OM. Expression of GFP-tagged POMP10 in inducible RNAi cell lines shows that its mitochondrial localization depends on pATOM36 but does not require Sam50 or ATOM40, the trypanosomal analogue of the Tom40 import pore. pATOM36 is a kinetoplastid-specific OM protein that has previously been implicated in the assembly of OM proteins and in mitochondrial DNA inheritance. In summary, our results show that although the features of the targeting signal in signal-anchored proteins are widely conserved, the protein machinery that mediates their biogenesis is not.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Julia
authors.initials: J
authors.lastname: Bruggisser
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Sandro
authors.initials: S
authors.lastname: Käser
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Mani
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland. Electronic address: andre.schneider@dcb.unibe.ch.
authors.forename: André
authors.initials: A
authors.lastname: Schneider
mesh_terms: D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000032:analysis / Q000378:metabolism*; D000072417:Protein Domains; D015800:Protozoan Proteins / Q000032:analysis / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D015800:Protozoan Proteins
keywords: Trypanosoma brucei; evolution; membrane biogenesis; mitochondrial transport; outer membrane