TOM9.2 Is a Calmodulin-Binding Protein Critical for TOM Complex Assembly but Not for Mitochondrial Protein Import in Arabidopsis thaliana

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.

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Cryo-EM structure of the mitochondrial protein-import channel TOM complex at near-atomic resolution

Nature Structural & Molecular Biology ◽

10.1038/s41594-019-0339-2 ◽

2019 ◽

Vol 26 (12) ◽

pp. 1158-1166 ◽

Cited By ~ 29

Author(s):

Kyle Tucker ◽

Eunyong Park

Keyword(s):

Protein Import ◽

Mitochondrial Protein ◽

Atomic Resolution ◽

Mitochondrial Protein Import ◽

Tom Complex

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Assembly of the Mitochondrial Protein Import Channel

Molecular Biology of the Cell ◽

10.1091/mbc.e10-06-0518 ◽

2010 ◽

Vol 21 (18) ◽

pp. 3106-3113 ◽

Cited By ~ 35

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.

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Functional Analysis of Human Metaxin in Mitochondrial Protein Import in Cultured Cells and Its Relationship with the Tom Complex

Biochemical and Biophysical Research Communications ◽

10.1006/bbrc.2000.3589 ◽

2000 ◽

Vol 276 (3) ◽

pp. 1028-1034 ◽

Cited By ~ 32

Author(s):

Khaleque Md. Abdul ◽

Kazutoyo Terada ◽

Masato Yano ◽

Michael T. Ryan ◽

Illo Streimann ◽

...

Keyword(s):

Functional Analysis ◽

Protein Import ◽

Cultured Cells ◽

Mitochondrial Protein ◽

Mitochondrial Protein Import ◽

Tom Complex

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Interplay between Mitochondrial Protein Import and Respiratory Complexes Assembly in Neuronal Health and Degeneration

Life ◽

10.3390/life11050432 ◽

2021 ◽

Vol 11 (5) ◽

pp. 432

Author(s):

Hope I. Needs ◽

Margherita Protasoni ◽

Jeremy M. Henley ◽

Julien Prudent ◽

Ian Collinson ◽

...

Keyword(s):

Protein Import ◽

Protein Translocation ◽

Mitochondrial Protein ◽

Nuclear Genome ◽

Mitochondrial Diseases ◽

Functional Protein ◽

Mitochondrial Protein Import ◽

Complex Assembly ◽

Respiratory Complex ◽

And Function

The fact that >99% of mitochondrial proteins are encoded by the nuclear genome and synthesised in the cytosol renders the process of mitochondrial protein import fundamental for normal organelle physiology. In addition to this, the nuclear genome comprises most of the proteins required for respiratory complex assembly and function. This means that without fully functional protein import, mitochondrial respiration will be defective, and the major cellular ATP source depleted. When mitochondrial protein import is impaired, a number of stress response pathways are activated in order to overcome the dysfunction and restore mitochondrial and cellular proteostasis. However, prolonged impaired mitochondrial protein import and subsequent defective respiratory chain function contributes to a number of diseases including primary mitochondrial diseases and neurodegeneration. This review focuses on how the processes of mitochondrial protein translocation and respiratory complex assembly and function are interlinked, how they are regulated, and their importance in health and disease.

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

10.1101/798371 ◽

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.

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Cytosolic ribosomes on the surface of mitochondria

10.1101/119339 ◽

2017 ◽

Author(s):

Vicki A. M. Gold ◽

Piotr Chroscicki ◽

Piotr Bragoszewski ◽

Agnieszka Chacinska

Keyword(s):

Protein Synthesis ◽

Spatial Organization ◽

Protein Import ◽

Mitochondrial Protein ◽

Mitochondrial Protein Import ◽

Tom Complex ◽

Nascent Chain ◽

Subtomogram Averaging ◽

Cytosolic Ribosomes

AbstractBy electron cryo-tomography and subtomogram averaging, translation-arrested ribosomes were used to depict the clustered organisation of the TOM complex on the surface of mitochondria, corroborating earlier reports of localized translation. Ribosomes were shown to interact specifically with the TOM complex and nascent chain binding was crucial for ribosome recruitment and stabilization. Ribosomes were bound to the membrane in discrete clusters, often in the vicinity of the crista junctions. This interaction highlights how protein synthesis may be coupled with transport, and the importance of spatial organization for efficient mitochondrial protein import.

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