Structure of the mitochondrial import gate reveals distinct preprotein paths

Araiso, Yuhei; Tsutsumi, Akihisa; Qiu, Jian; Imai, Keisuke; Shiota, Takuya; Song, Jiyao; Lindau, Caroline; Wenz, Lena Sophie; Sakaue, Haruka; Yunoki, Kaori; Kawano, Shin; Suzuki, Junko; Wischnewski, Marilena; Schütze, Conny; Ariyama, Hirotaka; Ando, Toshio; Becker, Thomas; Lithgow, Trevor; Wiedemann, Nils; Pfanner, Nikolaus; Kikkawa, Masahide; Endo, Toshiya

doi:10.1038/s41586-019-1680-7

Cited by 179 publications

(260 citation statements)

References 64 publications

Supporting

Mentioning

215

Contrasting

Unclassified

Order By: Relevance

“…The first transmembrane ahelix of Sam37 is well defined, spanning the membrane adjacent to the Sam50 b-barrel, but making no contact with the b-barrel. This contrasts with the recently reported high resolution structures of the TOM core complex, where transmembrane a-helices closely associate with the hydrophobic surface of the Tom40 b-barrel 25,26 . The linker that connects the two predicted transmembrane helices in Sam37 interacts with the Sam50 POTRA domain, contributing an additional anti-parallel b-strand to that domain.…”

Section: The Sam Complex Forms Dimers In Detergentcontrasting

confidence: 97%

“…This further validates the correctness of our model. Tom22 in the reported structures 25,26 is missing the cytosolic part, suggesting that this portion is very flexible. The Table 6).…”

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 90%

“…Based on these results, we modeled the Sam37-Tom22 interaction using a truncated sequence for MtTom22 (residues 55-135). While the transmembrane helix of ScTom22 has a known structure 25,26 , MtTom22 residues 55-85 were modeled ab-initio. The resulting MtTom22 in the context of the known ScTOM core complex 25,26 is an extended transmembrane a-helix with very limited degrees of freedom in the truncated cytosolic domain, which is positively charged.…”

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 99%

“…While the transmembrane helix of ScTom22 has a known structure 25,26 , MtTom22 residues 55-85 were modeled ab-initio. The resulting MtTom22 in the context of the known ScTOM core complex 25,26 is an extended transmembrane a-helix with very limited degrees of freedom in the truncated cytosolic domain, which is positively charged. Examining the surface charges in Sam37, we identified two negatively charged regions that could interact with MtTom22.…”

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 99%

“…In contrast to bacteria, mitochondria are predicted to make only four types of b-barrel outer membrane protein: Sam50, Tom40, VDAC, and Mdm10 24 . Structures of Tom40 25,26 and VDAC 27 reveal very similar 19-stranded b-barrel proteins; Mdm10 is expected to adopt the same fold. Therefore, it appears that Sam50 substrates may use a single folding and insertion mechanism.…”

mentioning

confidence: 97%

See 4 more Smart Citations

Structural Insight into Mitochondrial β-Barrel Outer Membrane Protein Biogenesis

Diederichs

Rollauer

et al. 2020

Preprint

View full text Add to dashboard Cite

In mitochondria, b-barrel outer membrane proteins mediate protein import, metabolite transport, lipid transport, and biogenesis. The Sorting and Assembly Machinery (SAM) complex consists of three proteins that assemble as a 1:1:1 complex to fold b-barrel proteins and insert them into the mitochondrial outer membrane. We report cryoEM structures of the SAM complex from Myceliophthora thermophila, which show that Sam50 forms a 16-stranded transmembrane b-barrel with a single polypeptide-transport-associated (POTRA) domain extending into the intermembrane space. Sam35 and Sam37 are located on the cytosolic side of the outer membrane, with Sam35 capping Sam50, and Sam37 interacting extensively with Sam35. Sam35 and Sam37 each adopt a GST-like fold, with no functional, structural, or sequence similarity to their bacterial counterparts. Structural analysis shows how the Sam50 bbarrel opens a lateral gate to accommodate its substrates. The SAM complex structure suggests how it interacts with other mitochondrial outer membrane proteins to create supercomplexes. components: a b-barrel core, Sam50, which spans the outer membrane, and two accessory subunits, Sam35 and Sam37, that associate with Sam50 on the cytosolic side of the membrane 2-5 . Sam50 and Sam35 are essential proteins, with Sam50 folding and inserting b-barrel substrates into the outer membrane and Sam35 interacting with the substrate b-signal located in the last b-strand 3 . Sam37, while not essential, functions in substrate release 3,6 and may also promote formation of a TOM-SAM supercomplex 7 .Bacterial b-barrel membrane proteins take a different pathway to reach the outer membrane, but they are inserted by evolutionarily related machinery 8 . In bacteria, proteins are synthesized in the cytoplasm, secreted across the inner membrane by the Sec translocon, bound to chaperones in the periplasm, and transferred to the Bacterial Assembly Machinery (BAM) complex for folding and insertion into the outer membrane 9,10 . In Escherichia coli, four lipoproteins, BamB, BamC, BamD, and BamE, associate with the periplasmic domain of BamA (itself a 16-stranded transmembrane b-barrel) to fold and insert b-barrels ranging in size and complexity from 8 b-strands with a simple barrel fold, to 26 b-strands with multiple domains 11 . Structures of BamA and BAM complexes illustrate two features of BamA that facilitate folding and insertion: [1] BamA has a narrowed hydrophobic surface where the first and last b-strands meet, which locally compresses and destabilizes the lipid bilayer to allow membrane protein insertion (BamA assisted model). [2] The first and last b-strands form a 'lateral gate' that has been shown to open and close by molecular dynamics (MD) simulations, disulfide crosslinking, and structures solved by X-ray crystallography and cryo-electron microscopy (cryoEM) 12-19 . The required opening and closing of the lateral gate gave rise to the budding model, where a b-

show abstract

Section: The Sam Complex Forms Dimers In Detergentcontrasting

confidence: 97%

“…This further validates the correctness of our model. Tom22 in the reported structures 25,26 is missing the cytosolic part, suggesting that this portion is very flexible. The Table 6).…”

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 90%

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 99%

Section: Molecular Modeling Of the Tom-sam Supercomplexmentioning

confidence: 99%

mentioning

confidence: 97%

See 3 more Smart Citations

Structural Insight into Mitochondrial β-Barrel Outer Membrane Protein Biogenesis

Diederichs

Rollauer

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

The proteasome: friend and foe of mitochondrial biogenesis

2020

View full text Add to dashboard Cite

Most mitochondrial proteins are synthesized in the cytosol and subsequently translocated as unfolded polypeptides into mitochondria. Cytosolic chaperones maintain precursor proteins in an import‐competent state. This post‐translational import reaction is under surveillance of the cytosolic ubiquitin‐proteasome system, which carries out several distinguishable activities. On the one hand, the proteasome degrades nonproductive protein precursors from the cytosol and nucleus, import intermediates that are stuck in mitochondrial translocases, and misfolded or damaged proteins from the outer membrane and the intermembrane space. These surveillance activities of the proteasome are essential for mitochondrial functionality, as well as cellular fitness and survival. On the other hand, the proteasome competes with mitochondria for nonimported cytosolic precursor proteins, which can compromise mitochondrial biogenesis. In order to balance the positive and negative effects of the cytosolic protein quality control system on mitochondria, mitochondrial import efficiency directly regulates the capacity of the proteasome via transcription factor Rpn4 in yeast and nuclear respiratory factor (Nrf) 1 and 2 in animal cells. In this review, we provide a thorough overview of how the proteasome regulates mitochondrial biogenesis.

show abstract

Mitochondrial protein import dysfunction: mitochondrial disease, neurodegenerative disease and cancer

2021

View full text Add to dashboard Cite

The majority of proteins localised to mitochondria are encoded by the nuclear genome, with approximately 1500 proteins imported into mammalian mitochondria. Dysfunction in this fundamental cellular process is linked to a variety of pathologies including neuropathies, cardiovascular disorders, myopathies, neurodegenerative diseases and cancer, demonstrating the importance of mitochondrial protein import machinery for cellular function. Correct import of proteins into mitochondria requires the co‐ordinated activity of multimeric protein translocation and sorting machineries located in both the outer and inner mitochondrial membranes, directing the imported proteins to the destined mitochondrial compartment. This dynamic process maintains cellular homeostasis, and its dysregulation significantly affects cellular signalling pathways and metabolism. This review summarises current knowledge of the mammalian mitochondrial import machinery and the pathological consequences of mutation of its components. In addition, we will discuss the role of mitochondrial import in cancer, and our current understanding of the role of mitochondrial import in neurodegenerative diseases including Alzheimer's disease, Huntington's disease and Parkinson's disease.

show abstract

Structure of the mitochondrial import gate reveals distinct preprotein paths

Cited by 179 publications

References 64 publications

Structural Insight into Mitochondrial β-Barrel Outer Membrane Protein Biogenesis

Structural Insight into Mitochondrial β-Barrel Outer Membrane Protein Biogenesis

The proteasome: friend and foe of mitochondrial biogenesis

Mitochondrial protein import dysfunction: mitochondrial disease, neurodegenerative disease and cancer

Contact Info

Product

Resources

About