Studies on Mitochondrial Proteins. II. Localization of Components in the inner membrane labelling with diazobenzenesulfonate, a non-penetrating probe

1974 ◽  
Vol 345 (1) ◽  
pp. 118-128 ◽  
Author(s):  
Harold M. Tinberg ◽  
Ronald L. Melnick ◽  
John Maguire ◽  
Lester Packer
Keyword(s):  
Mitochondrial Proteins ◽  
Inner Membrane

scholarly journals Monolysocardiolipin (MLCL) interactions with mitochondrial membrane proteins

2020 ◽  
Vol 48 (3) ◽  
pp. 993-1004
Author(s):  
Anna L. Duncan
Keyword(s):  
Protein Interactions ◽  
Mitochondrial Membrane ◽  
Barth Syndrome ◽  
Mitochondrial Proteins ◽  
Mitochondrial Membranes ◽  
Inner Membrane ◽  
Computational Approaches ◽  
Mitochondrial Inner Membrane ◽  
Recent Developments ◽  
The Stability

Monolysocardiolipin (MLCL) is a three-tailed variant of cardiolipin (CL), the signature lipid of mitochondria. MLCL is not normally found in healthy tissue but accumulates in mitochondria of people with Barth syndrome (BTHS), with an overall increase in the MLCL:CL ratio. The reason for MLCL accumulation remains to be fully understood. The effect of MLCL build-up and decreased CL content in causing the characteristics of BTHS are also unclear. In both cases, an understanding of the nature of MLCL interaction with mitochondrial proteins will be key. Recent work has shown that MLCL associates less tightly than CL with proteins in the mitochondrial inner membrane, suggesting that MLCL accumulation is a result of CL degradation, and that the lack of MLCL–protein interactions compromises the stability of the protein-dense mitochondrial inner membrane, leading to a decrease in optimal respiration. There is some data on MLCL–protein interactions for proteins involved in the respiratory chain and in apoptosis, but there remains much to be understood regarding the nature of MLCL–protein interactions. Recent developments in structural, analytical and computational approaches mean that these investigations are now possible. Such an understanding will be key to further insights into how MLCL accumulation impacts mitochondrial membranes. In turn, these insights will help to support the development of therapies for people with BTHS and give a broader understanding of other diseases involving defective CL content.

scholarly journals Protein translocation channel of mitochondrial inner membrane and matrix-exposed import motor communicate via two-domain coupling protein

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Rupa Banerjee ◽  
Christina Gladkova ◽  
Koyeli Mapa ◽  
Gregor Witte ◽  
Dejana Mokranjac
Keyword(s):  
Domain Structure ◽  
Protein Translocation ◽  
Mitochondrial Proteins ◽  
Inner Membrane ◽  
Terminal Domain ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Coupling Protein ◽  
Domain Coupling

The majority of mitochondrial proteins are targeted to mitochondria by N-terminal presequences and use the TIM23 complex for their translocation across the mitochondrial inner membrane. During import, translocation through the channel in the inner membrane is coupled to the ATP-dependent action of an Hsp70-based import motor at the matrix face. How these two processes are coordinated remained unclear. We show here that the two domain structure of Tim44 plays a central role in this process. The N-terminal domain of Tim44 interacts with the components of the import motor, whereas its C-terminal domain interacts with the translocation channel and is in contact with translocating proteins. Our data suggest that the translocation channel and the import motor of the TIM23 complex communicate through rearrangements of the two domains of Tim44 that are stimulated by translocating proteins.

scholarly journals Quality control of mitochondrial protein synthesis is required for membrane integrity and cell fitness

2015 ◽  
Vol 211 (2) ◽  
pp. 373-389 ◽  
Author(s):  
Uwe Richter ◽  
Taina Lahtinen ◽  
Paula Marttinen ◽  
Fumi Suomi ◽  
Brendan J. Battersby
Keyword(s):  
Quality Control ◽  
Protein Synthesis ◽  
Oxidative Phosphorylation ◽  
De Novo ◽  
Mitochondrial Protein ◽  
Membrane Integrity ◽  
Mitochondrial Proteins ◽  
Protein Accumulation ◽  
Mitochondrial Protein Synthesis ◽  
Inner Membrane

Mitochondrial ribosomes synthesize a subset of hydrophobic proteins required for assembly of the oxidative phosphorylation complexes. This process requires temporal and spatial coordination and regulation, so quality control of mitochondrial protein synthesis is paramount to maintain proteostasis. We show how impaired turnover of de novo mitochondrial proteins leads to aberrant protein accumulation in the mitochondrial inner membrane. This creates a stress in the inner membrane that progressively dissipates the mitochondrial membrane potential, which in turn stalls mitochondrial protein synthesis and fragments the mitochondrial network. The mitochondrial m-AAA protease subunit AFG3L2 is critical to this surveillance mechanism that we propose acts as a sensor to couple the synthesis of mitochondrial proteins with organelle fitness, thus ensuring coordinated assembly of the oxidative phosphorylation complexes from two sets of ribosomes.

scholarly journals Cooperation of translocase complexes in mitochondrial protein import

2007 ◽  
Vol 179 (4) ◽  
pp. 585-591 ◽  
Author(s):  
Stephan Kutik ◽  
Bernard Guiard ◽  
Helmut E. Meyer ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Protein Complexes ◽  
Mitochondrial Protein ◽  
Mitochondrial Proteins ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Precursor Proteins ◽  
Preprotein Translocation

Most mitochondrial proteins are synthesized in the cytosol and imported into one of the four mitochondrial compartments: outer membrane, intermembrane space, inner membrane, and matrix. Each compartment contains protein complexes that interact with precursor proteins and promote their transport. These translocase complexes do not act as independent units but cooperate with each other and further membrane complexes in a dynamic manner. We propose that a regulated coupling of translocases is important for the coordination of preprotein translocation and efficient sorting to intramitochondrial compartments.

scholarly journals Fates of Sec, Tat, and YidC Translocases in Mitochondria and Other Eukaryotic Compartments

2021 ◽  
Author(s):  
Markéta Petrů ◽  
Vít Dohnálek ◽  
Zoltán Füssy ◽  
Pavel Doležal
Keyword(s):  
Genetic Control ◽  
Mitochondrial Function ◽  
Protein Export ◽  
The Other ◽  
Mitochondrial Proteins ◽  
Endomembrane System ◽  
Inner Membrane ◽  
Bacterial Endosymbiont ◽  
Single Substrate ◽  
Host Nucleus

Abstract Formation of mitochondria by the conversion of a bacterial endosymbiont was a key moment in the evolution of eukaryotes. It was made possible by outsourcing the endosymbiont’s genetic control to the host nucleus, while developing the import machinery for proteins synthesized on cytosolic ribosomes. The original protein export machines of the nascent organelle remained to be repurposed or were completely abandoned. This review follows the evolutionary fates of three prokaryotic inner membrane translocases Sec, Tat, and YidC. Homologs of all three translocases can still be found in current mitochondria, but with different importance for mitochondrial function. Although the mitochondrial YidC homolog, Oxa1, became an omnipresent independent insertase, the other two remained only sporadically present in mitochondria. Only a single substrate is known for the mitochondrial Tat and no function has yet been assigned for the mitochondrial Sec. Finally, this review compares these ancestral mitochondrial proteins with their paralogs operating in the plastids and the endomembrane system.

scholarly journals Inhibition of the Mitochondrial Protein Import Machinery Is Selectively Cytotoxic to Acute Myeloid Leukemia (AML) Cells and Stem Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1572-1572 ◽  
Author(s):  
Danny V Jeyaraju ◽  
Veronique Voisin ◽  
Changjiang Xu ◽  
Rose Hurren ◽  
Marcela Gronda ◽  
...  
Keyword(s):  
Stem Cells ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Proteins ◽  
Leukemia Cells ◽  
Mitochondrial Protein Import ◽  
Normal Cells ◽  
Mitochondrial Stress ◽  
Inner Membrane ◽  
The Impact

Abstract A subset of AML and stem cells have increased mitochondrial stress and increased expression of mitochondrial proteases that degrade misfolded mitochondrial proteins. Given the recent findings of the interplay between mitochondrial homeostasis and mitochondrial protein import, we hypothesized that AML cells have an increased reliance on mitochondrial protein import as a compensatory mechanism for increased mitochondrial stress. To test this hypothesis, we measured expression levels of key mitochondrial protein import genes in publicly available datasets (GSE30377, GSE42414 and GSE 24759) and demonstrated their up regulation in a subset of AML cells over normal hematopoietic cells. Increased expression occurred across the spectrum of molecular mutations and cytogenetic abnormalities. Moreover, expression levels of mitochondrial protein import genes were enriched in functionally defined AML stem cells over bulk cells. To assess the impact of inhibiting mitochondrial protein import in AML, we knocked down the outer mitochondrial membrane import channel TOM40, the inner membrane import channel Tim23 and the oxidase ALR, that folds proteins through a disulfide relay system in the mitochondrial inner membrane space and is a rate limiting step for the import of a subset of mitochondrial proteins. Knockdown of these targets in OCI-AML2, TEX and U937 leukemia cells with shRNA reduced growth and viability of AML cells. Knockdown of ALR targeted the leukemia initiating cells as it abrogated engraftment of TEX leukemia cells into immune deficient mice (shRNA ALR = 5.481 +/- 0.9 % engraftment vs shRNA control= 29.44 +/- 5.4 % engraftment; p =0.0004) . Mechanistically, knockdown of mitochondrial import genes reduced levels of nuclear (ATP5A, SDHB and NDUFB8), but not mitochondrial (CoxII) encoded proteins of the OXPHOS chain. This in turn led to decreased basal oxygen consumption in leukemic cells. As a chemical approach to investigate the impact of inhibiting mitochondrial protein import in AML and normal cells, we tested the effects of MitoBloCK-6 and related analogues that selectively inhibit ALR in zebrafish, hESCs and yeast models. MitoBloCK-6 and related analogues killed leukemia cell lines (OCI-AML2, TEX, Jurkat and NB4) with an IC50of 5-10 µM. At these concentrations, MitoBloCK-6 decreased levels of nuclear (ATP5A, SDHB and NDUFB8), but not mitochondrial encoded (CoxII) proteins of the OXPHOS chain. Demonstrating the functional importance of changes in mitochondrial metabolism by these compounds, rho zero 143B rhabdomyosarcoma cells that lack mitochondrial DNA and rely solely on glycolysis were resistant to MitoBloCK-6. Finally, we tested the effects of MitoBloCK-6 on primary AML and normal cells. Treatment with MitoBloCK-6 (2 µM) inhibited clonogenic growth of (4 of 5) primary AML > 64% but produced <3% loss of clonogenic growth in normal hematopoietic cells. Finally, in an OCI-AML2 xenograft model, systemic administration of MitoBloCK-6 reduced tumor growth > 50% of control without toxicity. Thus, we have demonstrated that AML cells have a unique reliance on mitochondrial protein import and inhibition of this pathway may be a new therapeutic strategy to selectively target a subset of AML and AML stem cells. Disclosures Schimmer: Novartis: Honoraria.

scholarly journals Role of Tim17 in coupling the import motor to the translocation channel of the mitochondrial presequence translocase

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Keren Demishtein-Zohary ◽  
Umut Günsel ◽  
Milit Marom ◽  
Rupa Banerjee ◽  
Walter Neupert ◽  
...  
Keyword(s):  
Mitochondrial Proteins ◽  
Inner Membrane ◽  
The Matrix

The majority of mitochondrial proteins use N-terminal presequences for targeting to mitochondria and are translocated by the presequence translocase. During translocation, proteins, threaded through the channel in the inner membrane, are handed over to the import motor at the matrix face. Tim17 is an essential, membrane-embedded subunit of the translocase; however, its function is only poorly understood. Here, we functionally dissected its four predicted transmembrane (TM) segments. Mutations in TM1 and TM2 impaired the interaction of Tim17 with Tim23, component of the translocation channel, whereas mutations in TM3 compromised binding of the import motor. We identified residues in the matrix-facing region of Tim17 involved in binding of the import motor. Our results reveal functionally distinct roles of different regions of Tim17 and suggest how they may be involved in handing over the proteins, during their translocation into mitochondria, from the channel to the import motor of the presequence translocase.

scholarly journals Homologue replacement in the import motor of the mitochondrial inner membrane of trypanosomes

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Corinne von Känel ◽  
Sergio A Muñoz-Gómez ◽  
Silke Oeljeklaus ◽  
Christoph Wenger ◽  
Bettina Warscheid ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Driving Force ◽  
Protein Import ◽  
Normal Growth ◽  
Mitochondrial Proteins ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Bona Fide ◽  
J Domain ◽  
J Protein

Many mitochondrial proteins contain N-terminal presequences that direct them to the organelle. The main driving force for their translocation across the inner membrane is provided by the presequence translocase-associated motor (PAM) which contains the J-protein Pam18. Here, we show that in the PAM of Trypanosoma brucei the function of Pam18 has been replaced by the non-orthologous euglenozoan-specific J-protein TbPam27. TbPam27 is specifically required for the import of mitochondrial presequence-containing but not for carrier proteins. Similar to yeast Pam18, TbPam27 requires an intact J-domain to function. Surprisingly, T. brucei still contains a bona fide Pam18 orthologue that, while essential for normal growth, is not involved in protein import. Thus, during evolution of kinetoplastids, Pam18 has been replaced by TbPam27. We propose that this replacement is linked to the transition from two ancestral and functionally distinct TIM complexes, found in most eukaryotes, to the single bifunctional TIM complex present in trypanosomes.

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