The Mitochondrial Oxidase Assembly Protein1 (Oxa1) Insertase Forms a Membrane Pore in Lipid Bilayers

Krüger, Vivien; Deckers, Markus; Hildenbeutel, Markus; Laan, Martin van der; Hellmers, Maike; Dreker, Christina; Preuss, Marc; Herrmann, Johannes M.; Rehling, Peter; Wagner, Richard; Meinecke, Michael

doi:10.1074/jbc.m112.387563

Cited by 40 publications

(28 citation statements)

References 41 publications

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“…ZZ mitochondria by double-affinity chromatography followed by tobacco etch virus (TEV) protease cleavage (30). In brief, mitochondria were resuspended to a protein concentration of 10 mg/ml in buffer A (1% SDS, 10% [wt/vol] glycerol, 100 mM NaCl, 10 mM imidazole, 1 mM PMSF, 50 mM NaH 2 PO 4 ).…”

Section: Methodsmentioning

confidence: 99%

The Channel-Forming Sym1 Protein Is Transported by the TIM23 Complex in a Presequence-Independent Manner

Reinhold

Krüger

Meinecke

et al. 2012

Molecular and Cellular Biology

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fThe majority of multispanning inner mitochondrial membrane proteins utilize internal targeting signals, which direct them to the carrier translocase (TIM22 complex), for their import. MPV17 and its Saccharomyces cerevisiae orthologue Sym1 are multispanning inner membrane proteins of unknown function with an amino-terminal presequence that suggests they may be targeted to the mitochondria. Mutations affecting MPV17 are associated with mitochondrial DNA depletion syndrome (MDDS). Reconstitution of purified Sym1 into planar lipid bilayers and electrophysiological measurements have demonstrated that Sym1 forms a membrane pore. To address the biogenesis of Sym1, which oligomerizes in the inner mitochondrial membrane, we studied its import and assembly pathway. Sym1 forms a transport intermediate at the translocase of the outer membrane (TOM) complex. Surprisingly, Sym1 was not transported into mitochondria by an amino-terminal signal, and in contrast to what has been observed in carrier proteins, Sym1 transport and assembly into the inner membrane were independent of small translocase of mitochondrial inner membrane (TIM) and TIM22 complexes. Instead, Sym1 required the presequence of translocase for its biogenesis. Our analyses have revealed a novel transport mechanism for a polytopic membrane protein in which internal signals direct the precursor into the inner membrane via the TIM23 complex, indicating a presequence-independent function of this translocase.

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Section: Methodsmentioning

confidence: 99%

The Channel-Forming Sym1 Protein Is Transported by the TIM23 Complex in a Presequence-Independent Manner

Reinhold

Krüger

Meinecke

et al. 2012

Molecular and Cellular Biology

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“…Prior to presequence cleavage, Cox2 targeting of the membrane begins with the action of the membrane-associated translational activator Pet111, which recognizes the 5′ untranslated region of COX2 mRNA (13–16). Cotranslational insertion of the Cox2 N-terminal tail together with the first transmembrane span depends on the export machinery, Oxa1 (17–19). The peripheral inner membrane protein Mba1 cooperates with Oxa1 in the insertion of mitochondrial translation products (20–25).…”

Section: Introductionmentioning

confidence: 99%

Ribosome-Associated Mba1 Escorts Cox2 from Insertion Machinery to Maturing Assembly Intermediates

Lorenzi

Oeljeklaus

Ronsör

et al. 2016

Molecular and Cellular Biology

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The three conserved core subunits of the cytochrome c oxidase are encoded by mitochondria in close to all eukaryotes. The Cox2 subunit spans the inner membrane twice, exposing the N and C termini to the intermembrane space. For this, the N terminus is exported cotranslationally by Oxa1 and subsequently undergoes proteolytic maturation in Saccharomyces cerevisiae. Little is known about the translocation of the C terminus, but Cox18 has been identified to be a critical protein in this process. Here we find that the scaffold protein Cox20, which promotes processing of Cox2, is in complex with the ribosome receptor Mba1 and translating mitochondrial ribosomes in a Cox2-dependent manner. The Mba1-Cox20 complex accumulates when export of the C terminus of Cox2 is blocked by the loss of the Cox18 protein. While Cox20 engages with Cox18, Mba1 is no longer present at this stage. Our analyses indicate that Cox20 associates with nascent Cox2 and Mba1 to promote Cox2 maturation cotranslationally. We suggest that Mba1 stabilizes the Cox20-ribosome complex and supports the handover of Cox2 to the Cox18 tail export machinery.

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“…Oxa1 is the best characterized export component conserved among prokaryotic and eukaryotic organisms. This channel forming factor is in direct contact with the translating ribosome (74,75). Remarkably, Oxa1 is also involved in the export of inner membrane proteins that use the TIM23 complex for their partial translocation into the matrix.…”

Section: Specific Transport Pathways and Their Interplays With Major mentioning

confidence: 99%

Mitochondrial protein homeostasis

2013

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Mitochondria use 800-1,500 proteins to perform their biological functions in the eukaryotic cells. Distinct transport and sorting mechanisms are responsible for the delivery of proteins to the correct location within mitochondria. Mitochondrial proteins undergo processing events and form functional assemblies.Finally, non-functional proteins are cleared to maintain healthy mitochondria. We provide an overview of the processes collectively contributing to the maintenance of mitochondrial protein homeostasis, which is critical for cell physiology and survival.

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The Mitochondrial Oxidase Assembly Protein1 (Oxa1) Insertase Forms a Membrane Pore in Lipid Bilayers

Cited by 40 publications

References 41 publications

The Channel-Forming Sym1 Protein Is Transported by the TIM23 Complex in a Presequence-Independent Manner

The Channel-Forming Sym1 Protein Is Transported by the TIM23 Complex in a Presequence-Independent Manner

Ribosome-Associated Mba1 Escorts Cox2 from Insertion Machinery to Maturing Assembly Intermediates

Mitochondrial protein homeostasis

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