Unraveling the Protein Translocation Machinery in the Mitochondrial Inner Membrane

1996 ◽  
pp. 149-162
Author(s):  
Nafsika G. Kronidou ◽  
Martin Horst
Keyword(s):  
Protein Translocation ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

scholarly journals The J-related Segment of Tim44 Is Essential for Cell Viability: A Mutant Tim44 Remains in the Mitochondrial Import Site, but Inefficiently Recruits mtHsp70 and Impairs Protein Translocation

1999 ◽  
Vol 145 (5) ◽  
pp. 961-972 ◽  
Author(s):  
Alessio Merlin ◽  
Wolfgang Voos ◽  
Ammy C. Maarse ◽  
Michiel Meijer ◽  
Nikolaus Pfanner ◽  
...  
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Adaptor Protein ◽  
Dependent Manner ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
J Proteins

Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Δ18 in addition to the endogenous wild-type Tim44. Tim44Δ18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Δ18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Δ18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain.

scholarly journals Dynamic subcompartmentalization of the mitochondrial inner membrane

2006 ◽  
Vol 175 (2) ◽  
pp. 237-247 ◽  
Author(s):  
Frank Vogel ◽  
Carsten Bornhövd ◽  
Walter Neupert ◽  
Andreas S. Reichert
Keyword(s):  
Protein Translocation ◽  
Physiological State ◽  
Protein Composition ◽  
Protein Translation ◽  
Complex Iii ◽  
Mitochondrial Morphology ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Metabolite Exchange ◽  
The Individual

The inner membrane of mitochondria is organized in two morphologically distinct domains, the inner boundary membrane (IBM) and the cristae membrane (CM), which are connected by narrow, tubular cristae junctions. The protein composition of these domains, their dynamics, and their biogenesis and maintenance are poorly understood at the molecular level. We have used quantitative immunoelectron microscopy to determine the distribution of a collection of representative proteins in yeast mitochondria belonging to seven major processes: oxidative phosphorylation, protein translocation, metabolite exchange, mitochondrial morphology, protein translation, iron–sulfur biogenesis, and protein degradation. We show that proteins are distributed in an uneven, yet not exclusive, manner between IBM and CM. The individual distributions reflect the physiological functions of proteins. Moreover, proteins can redistribute between the domains upon changes of the physiological state of the cell. Impairing assembly of complex III affects the distribution of partially assembled subunits. We propose a model for the generation of this dynamic subcompartmentalization of the mitochondrial inner membrane.

scholarly journals tRNA import across the mitochondrial inner membrane in T. brucei requires TIM subunits but is independent of protein import

2020 ◽  
Vol 48 (21) ◽  
pp. 12269-12281
Author(s):  
Shikha Shikha ◽  
Jonathan L Huot ◽  
André Schneider ◽  
Moritz Niemann
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Matrix Proteins ◽  
Trna Genes ◽  
Mitochondrial Trna ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Trna Import ◽  
Inner Membrane Protein

Abstract Mitochondrial tRNA import is widespread, but mechanistic insights of how tRNAs are translocated across mitochondrial membranes remain scarce. The parasitic protozoan T. brucei lacks mitochondrial tRNA genes. Consequently, it imports all organellar tRNAs from the cytosol. Here we investigated the connection between tRNA and protein translocation across the mitochondrial inner membrane. Trypanosomes have a single inner membrane protein translocase that consists of three heterooligomeric submodules, which all are required for import of matrix proteins. In vivo depletion of individual submodules shows that surprisingly only the integral membrane core module, including the protein import pore, but not the presequence-associated import motor are required for mitochondrial tRNA import. Thus we could uncouple import of matrix proteins from import of tRNAs even though both substrates are imported into the same mitochondrial subcompartment. This is reminiscent to the outer membrane where the main protein translocase but not on-going protein translocation is required for tRNA import. We also show that import of tRNAs across the outer and inner membranes are coupled to each other. Taken together, these data support the ‘alternate import model’, which states that tRNA and protein import while mechanistically independent use the same translocation pores but not at the same time.

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 The non-canonical mitochondrial inner membrane presequence translocase of trypanosomatids contains two essential rhomboid-like proteins

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Anke Harsman ◽  
Silke Oeljeklaus ◽  
Christoph Wenger ◽  
Jonathan L. Huot ◽  
Bettina Warscheid ◽  
...  
Keyword(s):  
Pore Formation ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Carrier ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Carrier Protein ◽  
Compositional Variations

Abstract Mitochondrial protein import is essential for all eukaryotes. Here we show that the early diverging eukaryote Trypanosoma brucei has a non-canonical inner membrane (IM) protein translocation machinery. Besides TbTim17, the single member of the Tim17/22/23 family in trypanosomes, the presequence translocase contains nine subunits that co-purify in reciprocal immunoprecipitations and with a presequence-containing substrate that is trapped in the translocation channel. Two of the newly discovered subunits are rhomboid-like proteins, which are essential for growth and mitochondrial protein import. Rhomboid-like proteins were proposed to form the protein translocation pore of the ER-associated degradation system, suggesting that they may contribute to pore formation in the presequence translocase of T. brucei. Pulldown of import-arrested mitochondrial carrier protein shows that the carrier translocase shares eight subunits with the presequence translocase. This indicates that T. brucei may have a single IM translocase that with compositional variations mediates import of presequence-containing and carrier proteins.

scholarly journals Protein import into mitochondria: the requirement for external ATP is precursor-specific whereas intramitochondrial ATP is universally needed for translocation into the matrix.

1994 ◽  
Vol 5 (4) ◽  
pp. 465-474 ◽  
Author(s):  
C Wachter ◽  
G Schatz ◽  
B S Glick
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Inner Membrane ◽  
In Vitro System ◽  
Mitochondrial Inner Membrane ◽  
Precursor Proteins ◽  
The Matrix

ATP is needed for the import of precursor proteins into mitochondria. However, the role of ATP and its site of action have been unclear. We have now investigated the ATP requirements for protein import into the mitochondrial matrix. These experiments employed an in vitro system that allowed ATP levels to be manipulated both inside and outside the mitochondrial inner membrane. Our results indicate that there are two distinct ATP requirements for mitochondrial protein import. ATP in the matrix is always needed for complete import of precursor proteins into this compartment, even when the precursors are presented to mitochondria in an unfolded conformation. In contrast, the requirement for external ATP is precursor-specific; depletion of external ATP strongly inhibits import of some precursors but has little or no effect with other precursors. A requirement for external ATP can often be overcome by denaturing the precursor with urea. We suggest that external ATP promotes the release of precursors from cytosolic chaperones, whereas matrix ATP drives protein translocation across the inner membrane.

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