scholarly journals Biogenesis of Tom40, Core Component of the Tom Complex of Mitochondria

1999 ◽  
Vol 146 (2) ◽  
pp. 321-332 ◽  
Author(s):  
Doron Rapaport ◽  
Walter Neupert
Keyword(s):  
Outer Membrane ◽  
Initial Step ◽  
Terminal Segment ◽  
Mitochondrial Outer Membrane ◽  
Core Component ◽  
Core Element ◽  
The Core ◽  
Tom Complex ◽  
Partially Folded Conformation ◽  
Import Receptor

Tom40 is an essential component of the preprotein translocase of the mitochondrial outer membrane (TOM complex) in which it constitutes the core element of the protein conducting pore. We have investigated the biogenesis of Tom40. Tom40 is inserted into the outer membrane by the TOM complex. Initially, Tom40 is bound as a monomer at the mitochondrial surface. The import receptor Tom20 is involved in this initial step; it stimulates both binding and efficient insertion of the Tom40 precursor. This step is followed by the formation of a further intermediate at which the Tom40 precursor is partially inserted into the outer membrane. Finally, Tom40 is integrated into preexisting TOM complexes. Efficient import appears to require the Tom40 precursor to be in a partially folded conformation. Neither the NH2 nor the COOH termini are necessary to target Tom40 to the outer membrane. However, the NH2-terminal segment is required for Tom40 to become assembled into the TOM complex. A model for the biogenesis of Tom40 is presented.

scholarly journals The N-terminal domain of Tob55 has a receptor-like function in the biogenesis of mitochondrial β-barrel proteins

2006 ◽  
Vol 176 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Shukry J. Habib ◽  
Thomas Waizenegger ◽  
Agathe Niewienda ◽  
Stefan A. Paschen ◽  
Walter Neupert ◽  
...  
Keyword(s):  
Structure Function ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Wild Type ◽  
Core Component ◽  
The Core ◽  
Terminal Domain ◽  
Tom Complex ◽  
Specific Manner

β-Barrel proteins constitute a distinct class of mitochondrial outer membrane proteins. For import into mitochondria, their precursor forms engage the TOM complex. They are then relayed to the TOB complex, which mediates their insertion into the outer membrane. We studied the structure–function relationships of the core component of the TOB complex, Tob55. Tob55 precursors with deletions in the N-terminal domain were not affected in their targeting to and insertion into the mitochondrial outer membrane. Replacement of wild-type Tob55 by these deletion variants resulted in reduced growth of cells, and mitochondria isolated from such cells were impaired in their capacity to import β-barrel precursors. The purified N-terminal domain was able to bind β-barrel precursors in a specific manner. Collectively, these results demonstrate that the N-terminal domain of Tob55 recognizes precursors of β-barrel proteins. This recognition may contribute to the coupling of the translocation of β-barrel precursors across the TOM complex to their interaction with the TOB complex.

scholarly journals Dissecting the interactions of PINK1 with the TOM complex in depolarized mitochondria

2022 ◽  
Author(s):  
Klaudia Maruszczak ◽  
Martin Jung ◽  
Shafqat Rasool ◽  
Jean-Francois Trempe ◽  
Doron Rapaport
Keyword(s):  
Parkinson’S Disease ◽  
Outer Membrane ◽  
Molecular Mechanism ◽  
Mitochondrial Outer Membrane ◽  
Structural Protein ◽  
Mitochondria Dysfunction ◽  
Tom Complex ◽  
The Individual ◽  
Import Receptor

Mitochondria dysfunction is involved in the pathomechanism of many illnesses including Parkinson's disease. PINK1, which is mutated in some cases of familiar Parkinsonism, is a key component in the degradation of damaged mitochondria by mitophagy. The accumulation of PINK1 on the mitochondrial outer membrane (MOM) of compromised organelles is crucial for the induction of mitophagy, but the molecular mechanism of this process is still unresolved. Here, we investigate the association of PINK1 with the TOM complex. We demonstrate that PINK1 heavily relies on the import receptor TOM70 for its association with mitochondria and directly interacts with this receptor. The structural protein TOM7 appears to play only a moderate role in PINK1 association with the TOM complex, probably due to its role in stabilizing this complex. PINK1 requires the TOM40 pore lumen for its stable interaction with the TOM complex and apparently remains there during its further association with the MOM. Overall, this study provides new insights on the role of the individual TOM subunits in the association of PINK1 with the MOM of depolarized mitochondria.

scholarly journals Role of Phosphatidylethanolamine in the Biogenesis of Mitochondrial Outer Membrane Proteins

2013 ◽  
Vol 288 (23) ◽  
pp. 16451-16459 ◽  
Author(s):  
Thomas Becker ◽  
Susanne E. Horvath ◽  
Lena Böttinger ◽  
Natalia Gebert ◽  
Günther Daum ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Proper Function ◽  
Mitochondrial Outer Membrane ◽  
Tom Complex ◽  
Precursor Proteins ◽  
Helical Proteins ◽  
The Stability

The mitochondrial outer membrane contains proteinaceous machineries for the import and assembly of proteins, including TOM (translocase of the outer membrane) and SAM (sorting and assembly machinery). It has been shown that the dimeric phospholipid cardiolipin is required for the stability of TOM and SAM complexes and thus for the efficient import and assembly of β-barrel proteins and some α-helical proteins of the outer membrane. Here, we report that mitochondria deficient in phosphatidylethanolamine (PE), the second non-bilayer-forming phospholipid, are impaired in the biogenesis of β-barrel proteins, but not of α-helical outer membrane proteins. The stability of TOM and SAM complexes is not disturbed by the lack of PE. By dissecting the import steps of β-barrel proteins, we show that an early import stage involving translocation through the TOM complex is affected. In PE-depleted mitochondria, the TOM complex binds precursor proteins with reduced efficiency. We conclude that PE is required for the proper function of the TOM complex.

scholarly journals Disordered clusters of Bak dimers rupture mitochondria during apoptosis

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Rachel T Uren ◽  
Martin O’Hely ◽  
Sweta Iyer ◽  
Ray Bartolo ◽  
Melissa X Shi ◽  
...  
Keyword(s):  
Linkage Analysis ◽  
Outer Membrane ◽  
Structural Heterogeneity ◽  
Mitochondrial Outer Membrane ◽  
Protein Interface ◽  
Unknown Mechanism ◽  
The Core ◽  
Mathematical Simulations ◽  
N Terminus ◽  
Comprehensive Survey

During apoptosis, Bak and Bax undergo major conformational change and form symmetric dimers that coalesce to perforate the mitochondrial outer membrane via an unknown mechanism. We have employed cysteine labelling and linkage analysis to the full length of Bak in mitochondria. This comprehensive survey showed that in each Bak dimer the N-termini are fully solvent-exposed and mobile, the core is highly structured, and the C-termini are flexible but restrained by their contact with the membrane. Dimer-dimer interactions were more labile than the BH3:groove interaction within dimers, suggesting there is no extensive protein interface between dimers. In addition, linkage in the mobile Bak N-terminus (V61C) specifically quantified association between dimers, allowing mathematical simulations of dimer arrangement. Together, our data show that Bak dimers form disordered clusters to generate lipidic pores. These findings provide a molecular explanation for the observed structural heterogeneity of the apoptotic pore.

scholarly journals Multispan mitochondrial outer membrane protein Ugo1 follows a unique Mim1-dependent import pathway

2011 ◽  
Vol 194 (3) ◽  
pp. 397-405 ◽  
Author(s):  
Dražen Papić ◽  
Katrin Krumpe ◽  
Jovana Dukanovic ◽  
Kai S. Dimmer ◽  
Doron Rapaport
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Gel Electrophoresis ◽  
Mitochondrial Outer Membrane ◽  
Yeast Mitochondria ◽  
Membrane Complex ◽  
Native Gel ◽  
Insertion Process ◽  
Import Receptor

The mitochondrial outer membrane (MOM) harbors several multispan proteins that execute various functions. Despite their importance, the mechanisms by which these proteins are recognized and inserted into the outer membrane remain largely unclear. In this paper, we address this issue using yeast mitochondria and the multispan protein Ugo1. Using a specific insertion assay and analysis by native gel electrophoresis, we show that the import receptor Tom70, but not its partner Tom20, is involved in the initial recognition of the Ugo1 precursor. Surprisingly, the import pore formed by the translocase of the outer membrane complex appears not to be required for the insertion process. Conversely, the multifunctional outer membrane protein mitochondrial import 1 (Mim1) plays a central role in mediating the insertion of Ugo1. Collectively, these results suggest that Ugo1 is inserted into the MOM by a novel pathway in which Tom70 and Mim1 contribute to the efficiency and selectivity of the process.

scholarly journals Role of the intermembrane-space domain of the preprotein receptor Tom22 in protein import into mitochondria.

1996 ◽  
Vol 16 (8) ◽  
pp. 4035-4042 ◽  
Author(s):  
D A Court ◽  
F E Nargang ◽  
H Steiner ◽  
R S Hodges ◽  
W Neupert ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Protein Translocation ◽  
Specific Binding ◽  
Mitochondrial Outer Membrane ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Terminal Domain ◽  
Tom Complex

Tom22 is an essential component of the protein translocation complex (Tom complex) of the mitochondrial outer membrane. The N-terminal domain of Tom22 functions as a preprotein receptor in cooperation with Tom20. The role of the C-terminal domain of Tom22, which is exposed to the intermembrane space (IMS), in its own assembly into the Tom complex and in the import of other preproteins was investigated. The C-terminal domain of Tom22 is not essential for the targeting and assembly of this protein, as constructs lacking part or all of the IMS domain became imported into mitochondria and assembled into the Tom complex. Mutant strains of Neurospora expressing the truncated Tom22 proteins were generated by a novel procedure. These mutants displayed wild-type growth rates, in contrast to cells lacking Tom22, which are not viable. The import of proteins into the outer membrane and the IMS of isolated mutant mitochondria was not affected. Some but not all preproteins destined for the matrix and inner membrane were imported less efficiently. The reduced import was not due to impaired interaction of presequences with their specific binding site on the trans side of the outer membrane. Rather, the IMS domain of Tom22 appears to slightly enhance the efficiency of the transfer of these preproteins to the import machinery of the inner membrane.

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.

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