scholarly journals Characterization of Rat TOM40, a Central Component of the Preprotein Translocase of the Mitochondrial Outer Membrane

2000 ◽  
Vol 275 (48) ◽  
pp. 37930-37936 ◽  
Author(s):  
Hiroyuki Suzuki ◽  
Yoshikazu Okazawa ◽  
Tohru Komiya ◽  
Kazuko Saeki ◽  
Eisuke Mekada ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Central Component

Further Characterization of Mitochondrial Outer Membrane: Evidence for the Presence of Two Endogenous Sialylated Glycoproteins1

1994 ◽  
Vol 116 (3) ◽  
pp. 643-648 ◽  
Author(s):  
Françcoise Gasnier ◽  
Dominique Ardail ◽  
Fabienne Lermé ◽  
Cédric Simonot ◽  
Elisabeth Vaganay ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane

scholarly journals Regulation of mitochondrial fusion by the F-box protein Mdm30 involves proteasome-independent turnover of Fzo1

2006 ◽  
Vol 173 (5) ◽  
pp. 645-650 ◽  
Author(s):  
Mafalda Escobar-Henriques ◽  
Benedikt Westermann ◽  
Thomas Langer
Keyword(s):  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Critical Role ◽  
Mitochondrial Fusion ◽  
Yeast Cells ◽  
Mitochondrial Outer Membrane ◽  
Central Component ◽  
Mitochondrial Morphology ◽  
Proteolytic Pathway ◽  
F Box Protein

Mitochondrial morphology depends on balanced fusion and fission events. A central component of the mitochondrial fusion apparatus is the conserved GTPase Fzo1 in the outer membrane of mitochondria. Mdm30, an F-box protein required for mitochondrial fusion in vegetatively growing cells, affects the cellular Fzo1 concentration in an unknown manner. We demonstrate that mitochondrial fusion requires a tight control of Fzo1 levels, which is ensured by Fzo1 turnover. Mdm30 binds to Fzo1 and, dependent on its F-box, mediates proteolysis of Fzo1. Unexpectedly, degradation occurs along a novel proteolytic pathway not involving ubiquitylation, Skp1–Cdc53–F-box (SCF) E3 ubiquitin ligase complexes, or 26S proteasomes, indicating a novel function of an F-box protein. This contrasts to the ubiquitin- and proteasome-dependent turnover of Fzo1 in α-factor–arrested yeast cells. Our results therefore reveal not only a critical role of Fzo1 degradation for mitochondrial fusion in vegetatively growing cells but also the existence of two distinct proteolytic pathways for the turnover of mitochondrial outer membrane proteins.

scholarly journals Genetic and Functional Interactions between the Mitochondrial Outer Membrane Proteins Tom6 and Sam37

2009 ◽  
Vol 29 (22) ◽  
pp. 5975-5988 ◽  
Author(s):  
Jovana Dukanovic ◽  
Kai S. Dimmer ◽  
Nathalie Bonnefoy ◽  
Katrin Krumpe ◽  
Doron Rapaport
Keyword(s):  
Outer Membrane ◽  
Elevated Temperatures ◽  
Genetic Interaction ◽  
Outer Membrane Proteins ◽  
Small Subunit ◽  
Mitochondrial Outer Membrane ◽  
Central Component ◽  
Entry Site ◽  
Tom Complex ◽  
Improved Stability

ABSTRACT The TOM complex is the general mitochondrial entry site for newly synthesized proteins. Precursors of β-barrel proteins initially follow this common pathway and are then relayed to the SAM/TOB complex, which mediates their integration into the outer membrane. Three proteins, Sam50 (Tob55), Sam35 (Tob38/Tom38), and Sam37 (Mas37), have been identified as the core constituents of the latter complex. Sam37 is essential for growth at elevated temperatures, but the function of the protein is currently unresolved. To identify interacting partners of Sam37 and thus shed light on its function, we screened for multicopy suppressors of sam37Δ. We identified the small subunit of the TOM complex, Tom6, as such a suppressor and found a tight genetic interaction between the two proteins. Overexpression of SAM37 suppresses the growth phenotype of tom6Δ, and cells lacking both genes are not viable. The ability of large amounts of Tom6 to suppress the sam37Δ phenotype can be linked to the capacity of Tom6 to stabilize Tom40, an essential β-barrel protein which is the central component of the TOM complex. Our results suggest that Sam37 is required for growth at higher temperatures, since it enhances the biogenesis of Tom40, and this requirement can be overruled by improved stability of newly synthesized Tom40 molecules.

scholarly journals Assembly of outer-membrane proteins in bacteria and mitochondria

Microbiology ◽  
2010 ◽  
Vol 156 (9) ◽  
pp. 2587-2596 ◽  
Author(s):  
Jan Tommassen
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Outer Membrane Proteins ◽  
Basic Mechanism ◽  
Eukaryotic Cell ◽  
Mitochondrial Outer Membrane ◽  
Central Component ◽  
Cell Organelles ◽  
C Terminus

The cell envelope of Gram-negative bacteria consists of two membranes separated by the periplasm. In contrast with most integral membrane proteins, which span the membrane in the form of hydrophobic α-helices, integral outer-membrane proteins (OMPs) form β-barrels. Similar β-barrel proteins are found in the outer membranes of mitochondria and chloroplasts, probably reflecting the endosymbiont origin of these eukaryotic cell organelles. How these β-barrel proteins are assembled into the outer membrane has remained enigmatic for a long time. In recent years, much progress has been reached in this field by the identification of the components of the OMP assembly machinery. The central component of this machinery, called Omp85 or BamA, is an essential and highly conserved bacterial protein that recognizes a signature sequence at the C terminus of its substrate OMPs. A homologue of this protein is also found in mitochondria, where it is required for the assembly of β-barrel proteins into the outer membrane as well. Although accessory components of the machineries are different between bacteria and mitochondria, a mitochondrial β-barrel OMP can be assembled into the bacterial outer membrane and, vice versa, bacterial OMPs expressed in yeast are assembled into the mitochondrial outer membrane. These observations indicate that the basic mechanism of OMP assembly is evolutionarily highly conserved.

scholarly journals Characterization of the signal that directs Bcl-xL, but not Bcl-2, to the mitochondrial outer membrane

2003 ◽  
Vol 160 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Thomas Kaufmann ◽  
Sarah Schlipf ◽  
Javier Sanz ◽  
Karin Neubert ◽  
Reuven Stein ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Targeting ◽  
Mitochondrial Localization ◽  
Intracellular Membranes ◽  
Bona Fide ◽  
Targeting Signal ◽  
Tm Domain ◽  
Mitochondrial Targeting Sequences

It is assumed that the survival factors Bcl-2 and Bcl-xL are mainly functional on mitochondria and therefore must contain mitochondrial targeting sequences. Here we show, however, that only Bcl-xL is specifically targeted to the mitochondrial outer membrane (MOM) whereas Bcl-2 distributes on several intracellular membranes. Mitochondrial targeting of Bcl-xL requires the COOH-terminal transmembrane (TM) domain flanked at both ends by at least two basic amino acids. This sequence is a bona fide targeting signal for the MOM as it confers specific mitochondrial localization to soluble EGFP. The signal is present in numerous proteins known to be directed to the MOM. Bcl-2 lacks the signal and therefore localizes to several intracellular membranes. The COOH-terminal region of Bcl-2 can be converted into a targeting signal for the MOM by increasing the basicity surrounding its TM. These data define a new targeting sequence for the MOM and propose that Bcl-2 acts on several intracellular membranes whereas Bcl-xL specifically functions on the MOM.

scholarly journals Characterization of a novel β-barrel protein (AtOM47) from the mitochondrial outer membrane ofArabidopsis thaliana

2016 ◽  
Vol 67 (21) ◽  
pp. 6061-6075 ◽  
Author(s):  
Lu Li ◽  
Szymon Kubiszewski-Jakubiak ◽  
Jordan Radomiljac ◽  
Yan Wang ◽  
Simon R. Law ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Ofarabidopsis Thaliana
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