scholarly journals Mitochondrial Protein Import

2004 ◽  
Vol 279 (44) ◽  
pp. 45701-45707 ◽  
Author(s):  
Masatoshi Esaki ◽  
Hidaka Shimizu ◽  
Tomoko Ono ◽  
Hayashi Yamamoto ◽  
Takashi Kanamori ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Protein Import ◽  
Tom Complex ◽  
Membrane Complex ◽  
Cytosolic Side

Protein translocation across the outer mitochondrial membrane is mediated by the translocator called the TOM (translocase of the outer mitochondrial membrane) complex. The TOM complex possesses two presequence binding sites on the cytosolic side (thecissite) and on the intermembrane space side (thetranssite). Here we analyzed the requirement of presequence elements and subunits of the TOM complex for presequence binding to thecisandtranssites of the TOM complex. The N-terminal 14 residues of the presequence of subunit 9 of F0-ATPase are required for binding to thetranssite. The interaction between the presequence and thecissite is not sufficient to anchor the precursor protein to the TOM complex. Tom7 constitutes or is close to thetranssite and has overlapping functions with the C-terminal intermembrane space domain of Tom22 in the mitochondrial protein import.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

Msp1/ATAD1 in Protein Quality Control and Regulation of Synaptic Activities

2020 ◽  
Vol 36 (1) ◽  
pp. 141-164
Author(s):  
Lan Wang ◽  
Peter Walter
Keyword(s):  
Quality Control ◽  
Mitochondrial Membrane ◽  
Protein Import ◽  
Protein Quality ◽  
Atp Hydrolysis ◽  
Mitochondrial Protein ◽  
Neurotransmitter Receptors ◽  
Functional Specialization ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Protein Import

Mitochondrial function depends on the efficient import of proteins synthesized in the cytosol. When cells experience stress, the efficiency and faithfulness of the mitochondrial protein import machinery are compromised, leading to homeostatic imbalances and damage to the organelle. Yeast Msp1 (mitochondrial sorting of proteins 1) and mammalian ATAD1 (ATPase family AAA domain–containing 1) are orthologous AAA proteins that, fueled by ATP hydrolysis, recognize and extract mislocalized membrane proteins from the outer mitochondrial membrane. Msp1 also extracts proteins that have become stuck in the import channel. The extracted proteins are targeted for proteasome-dependent degradation or, in the case of mistargeted tail-anchored proteins, are given another chance to be routed correctly. In addition, ATAD1 is implicated in the regulation of synaptic plasticity, mediating the release of neurotransmitter receptors from postsynaptic scaffolds to allow their trafficking. Here we discuss how structural and functional specialization imparts the unique properties that allow Msp1/ATAD1 ATPases to fulfill these diverse functions and also highlight outstanding questions in the field.

scholarly journals Tim23–Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import

2009 ◽  
Vol 184 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Yasushi Tamura ◽  
Yoshihiro Harada ◽  
Takuya Shiota ◽  
Koji Yamano ◽  
Kazuaki Watanabe ◽  
...  
Keyword(s):  
Motor Proteins ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
The Matrix ◽  
General Protein ◽  
Mitochondrial Hsp70

Mitochondrial protein traffic requires coordinated operation of protein translocator complexes in the mitochondrial membrane. The TIM23 complex translocates and inserts proteins into the mitochondrial inner membrane. Here we analyze the intermembrane space (IMS) domains of Tim23 and Tim50, which are essential subunits of the TIM23 complex, in these functions. We find that interactions of Tim23 and Tim50 in the IMS facilitate transfer of precursor proteins from the TOM40 complex, a general protein translocator in the outer membrane, to the TIM23 complex. Tim23–Tim50 interactions also facilitate a late step of protein translocation across the inner membrane by promoting motor functions of mitochondrial Hsp70 in the matrix. Therefore, the Tim23–Tim50 pair coordinates the actions of the TOM40 and TIM23 complexes together with motor proteins for mitochondrial protein import.

scholarly journals Assembly of the Mitochondrial Protein Import Channel

2010 ◽  
Vol 21 (18) ◽  
pp. 3106-3113 ◽  
Author(s):  
Thomas Becker ◽  
Bernard Guiard ◽  
Nicolas Thornton ◽  
Nicole Zufall ◽  
David A. Stroud ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Insertion ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Protein Import ◽  
Transmembrane Segments ◽  
Tom Complex ◽  
Assembly Pathway ◽  
Assembly Defect

The preprotein translocase of the outer mitochondrial membrane (TOM) consists of a central β-barrel channel, Tom40, and six proteins with α-helical transmembrane segments. The precursor of Tom40 is imported from the cytosol by a pre-existing TOM complex and inserted into the outer membrane by the sorting and assembly machinery (SAM). Tom40 then assembles with α-helical Tom proteins to the mature TOM complex. The outer membrane protein Mim1 promotes membrane insertion of several α-helical Tom proteins but also affects the biogenesis of Tom40 by an unknown mechanism. We have identified a novel intermediate in the assembly pathway of Tom40, revealing a two-stage interaction of the precursor with the SAM complex. The second SAM stage represents assembly of Tom5 with the precursor of Tom40. Mim1-deficient mitochondria accumulate Tom40 at the first SAM stage like Tom5-deficient mitochondria. Tom5 promotes formation of the second SAM stage and thus suppresses the Tom40 assembly defect of mim1Δ mitochondria. We conclude that the assembly of newly imported Tom40 is directly initiated at the SAM complex by its association with Tom5. The involvement of Mim1 in Tom40 biogenesis can be largely attributed to its role in import of Tom5.

scholarly journals A Biochemical and Structural Understanding of TOM Complex Interactions and Implications for Human Health and Disease

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1164
Author(s):  
Ashley S. Pitt ◽  
Susan K. Buchanan
Keyword(s):  
Human Health ◽  
Mitochondrial Membrane ◽  
Cancer Metabolism ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Outer Mitochondrial Membrane ◽  
Tom Complex ◽  
Complex Interactions ◽  
Health And Disease ◽  
Function Relationship

The central role mitochondria play in cellular homeostasis has made its study critical to our understanding of various aspects of human health and disease. Mitochondria rely on the translocase of the outer membrane (TOM) complex for the bulk of mitochondrial protein import. In addition to its role as the major entry point for mitochondrial proteins, the TOM complex serves as an entry pathway for viral proteins. TOM complex subunits also participate in a host of interactions that have been studied extensively for their function in neurodegenerative diseases, cardiovascular diseases, innate immunity, cancer, metabolism, mitophagy and autophagy. Recent advances in our structural understanding of the TOM complex and the protein import machinery of the outer mitochondrial membrane have made structure-based therapeutics targeting outer mitochondrial membrane proteins during mitochondrial dysfunction an exciting prospect. Here, we describe advances in understanding the TOM complex, the interactome of the TOM complex subunits, the implications for the development of therapeutics, and our understanding of the structure/function relationship between components of the TOM complex and mitochondrial homeostasis.

scholarly journals A disulfide bond in the TIM23 complex is crucial for voltage gating and mitochondrial protein import

2016 ◽  
Vol 214 (4) ◽  
pp. 417-431 ◽  
Author(s):  
Ajay Ramesh ◽  
Valentina Peleh ◽  
Sonia Martinez-Caballero ◽  
Florian Wollweber ◽  
Frederik Sommer ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Voltage Gating ◽  
Intermembrane Space ◽  
Sulfhydryl Oxidase ◽  
Mitochondrial Protein Import ◽  
Conducting Channel ◽  
Oxidoreductase Activity

Tim17 is a central, membrane-embedded subunit of the mitochondrial protein import machinery. In this study, we show that Tim17 contains a pair of highly conserved cysteine residues that form a structural disulfide bond exposed to the intermembrane space (IMS). This disulfide bond is critical for efficient protein translocation through the TIM23 complex and for dynamic gating of its preprotein-conducting channel. The disulfide bond in Tim17 is formed during insertion of the protein into the inner membrane. Whereas the import of Tim17 depends on the binding to the IMS protein Mia40, the oxidoreductase activity of Mia40 is surprisingly dispensable for Tim17 oxidation. Our observations suggest that Tim17 can be directly oxidized by the sulfhydryl oxidase Erv1. Thus, import and oxidation of Tim17 are mediated by the mitochondrial disulfide relay, though the mechanism by which the disulfide bond in Tim17 is formed differs considerably from that of soluble IMS proteins.

scholarly journals Cryo-EM structure of the mitochondrial protein-import channel TOM complex from Saccharomyces cerevisiae

2019 ◽  
Author(s):  
Kyle Tucker ◽  
Eunyong Park
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Nuclear Genome ◽  
Molecular Organization ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Protein Import ◽  
Tom Complex ◽  
Polar Interactions

AbstractNearly all mitochondrial proteins are encoded by the nuclear genome and imported into mitochondria following synthesis on cytosolic ribosomes. These precursor proteins are translocated into mitochondria by the TOM complex, a protein-conducting channel in the mitochondrial outer membrane. Using cryo-EM, we have obtained high-resolution structures of both apo and presequence-bound core TOM complexes from Saccharomyces cerevisiae in dimeric and tetrameric forms. Dimeric TOM consists of two copies each of five proteins arranged in two-fold symmetry—Tom40, a pore-forming β-barrel with an overall negatively-charged inner surface, and four auxiliary α-helical transmembrane proteins. The structure suggests that presequences for mitochondrial targeting insert into the Tom40 channel mainly by electrostatic and polar interactions. The tetrameric complex is essentially a dimer of dimeric TOM, which may be capable of forming higher-order oligomers. Our study reveals the molecular organization of the TOM complex and provides new insights about the mechanism of protein translocation into mitochondria.

scholarly journals Tim50’s presequence receptor domain is essential for signal driven transport across the TIM23 complex

2011 ◽  
Vol 195 (4) ◽  
pp. 643-656 ◽  
Author(s):  
Christian Schulz ◽  
Oleksandr Lytovchenko ◽  
Jonathan Melin ◽  
Agnieszka Chacinska ◽  
Bernard Guiard ◽  
...  
Keyword(s):  
Binding Sites ◽  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Proteins ◽  
Outer Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Protein Import ◽  
Targeting Signals ◽  
Receptor Domain

N-terminal targeting signals (presequences) direct proteins across the TOM complex in the outer mitochondrial membrane and the TIM23 complex in the inner mitochondrial membrane. Presequences provide directionality to the transport process and regulate the transport machineries during translocation. However, surprisingly little is known about how presequence receptors interact with the signals and what role these interactions play during preprotein transport. Here, we identify signal-binding sites of presequence receptors through photo-affinity labeling. Using engineered presequence probes, photo cross-linking sites on mitochondrial proteins were mapped mass spectrometrically, thereby defining a presequence-binding domain of Tim50, a core subunit of the TIM23 complex that is essential for mitochondrial protein import. Our results establish Tim50 as the primary presequence receptor at the inner membrane and show that targeting signals and Tim50 regulate the Tim23 channel in an antagonistic manner.

Porins as helpers in mitochondrial protein translocation

2020 ◽  
Vol 401 (6-7) ◽  
pp. 699-708 ◽  
Author(s):  
Alexander Grevel ◽  
Thomas Becker
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Anion Channel ◽  
Intermembrane Space ◽  
Voltage Dependent Anion Channel ◽  
Entry Site ◽  
Inner Membrane ◽  
Tom Complex

AbstractMitochondria import the vast majority of their proteins via dedicated protein machineries. The translocase of the outer membrane (TOM complex) forms the main entry site for precursor proteins that are produced on cytosolic ribosomes. Subsequently, different protein sorting machineries transfer the incoming preproteins to the mitochondrial outer and inner membranes, the intermembrane space, and the matrix. In this review, we highlight the recently discovered role of porin, also termed voltage-dependent anion channel (VDAC), in mitochondrial protein biogenesis. Porin forms the major channel for metabolites and ions in the outer membrane of mitochondria. Two different functions of porin in protein translocation have been reported. First, it controls the formation of the TOM complex by modulating the integration of the central receptor Tom22 into the mature translocase. Second, porin promotes the transport of carrier proteins toward the carrier translocase (TIM22 complex), which inserts these preproteins into the inner membrane. Therefore, porin acts as a coupling factor to spatially coordinate outer and inner membrane transport steps. Thus, porin links metabolite transport to protein import, which are both essential for mitochondrial function and biogenesis.

scholarly journals A discrete pathway for the transfer of intermembrane space proteins across the outer membrane of mitochondria

2014 ◽  
Vol 25 (25) ◽  
pp. 3999-4009 ◽  
Author(s):  
Agnieszka Gornicka ◽  
Piotr Bragoszewski ◽  
Piotr Chroscicki ◽  
Lena-Sophie Wenz ◽  
Christian Schulz ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Membrane ◽  
Alternative Pathway ◽  
Intermembrane Space ◽  
Outer Mitochondrial Membrane ◽  
Membrane Translocation ◽  
Tom Complex ◽  
Precursor Proteins ◽  
Core Components

Mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria with the help of protein translocases. For the majority of precursor proteins, the role of the translocase of the outer membrane (TOM) and mechanisms of their transport across the outer mitochondrial membrane are well recognized. However, little is known about the mode of membrane translocation for proteins that are targeted to the intermembrane space via the redox-driven mitochondrial intermembrane space import and assembly (MIA) pathway. On the basis of the results obtained from an in organello competition import assay, we hypothesized that MIA-dependent precursor proteins use an alternative pathway to cross the outer mitochondrial membrane. Here we demonstrate that this alternative pathway involves the protein channel formed by Tom40. We sought a translocation intermediate by expressing tagged versions of MIA-dependent proteins in vivo. We identified a transient interaction between our model substrates and Tom40. Of interest, outer membrane translocation did not directly involve other core components of the TOM complex, including Tom22. Thus MIA-dependent proteins take another route across the outer mitochondrial membrane that involves Tom40 in a form that is different from the canonical TOM complex.

Sign in / Sign up

Export Citation Format

Share Document