scholarly journals A crucial role of the mitochondrial protein import receptor MOM19 for the biogenesis of mitochondria

1994 ◽  
Vol 124 (5) ◽  
pp. 637-648 ◽  
Author(s):  
TA Harkness ◽  
FE Nargang ◽  
I van der Klei ◽  
W Neupert ◽  
R Lill
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Outer Membrane ◽  
Growth Defect ◽  
The Novel ◽  
Genetic Method ◽  
Severe Growth Defect ◽  
Biogenesis Of Mitochondria ◽  
Import Receptor

The novel genetic method of "sheltered RIP" (repeat induced point mutation) was used to generate a Neurospora crassa mutant in which MOM19, a component of the protein import machinery of the mitochondrial outer membrane, can be depleted. Deficiency in MOM19 resulted in a severe growth defect, but the cells remained viable. The number of mitochondrial profiles was not grossly changed, but mutant mitochondria were highly deficient in cristae membranes, cytochromes, and protein synthesis activity. Protein import into isolated mutant mitochondria was decreased by factors of 6 to 30 for most proteins from all suborganellar compartments. Proteins like the ADP/ATP carrier, MOM19, and cytochrome c, whose import into wild-type mitochondria occurs independently of MOM19 became imported normally showing that the reduced import activities are solely caused by a lack of MOM19. Depletion of MOM19 reveals a close functional relationship between MOM19 and MOM22, since loss of MOM19 led to decreased levels of MOM22 and reduced protein import through MOM22. Furthermore, MOM72 does not function as a general backup receptor for MOM19 suggesting that these two proteins have distinct precursor specificities. These findings demonstrate that the import receptor MOM19 fulfills an important role in the biogenesis of mitochondria and that it is essential for the formation of mitochondria competent in respiration and phosphorylation.

scholarly journals Human mitochondrial import receptor Tom70 functions as a monomer

2010 ◽  
Vol 429 (3) ◽  
pp. 553-563 ◽  
Author(s):  
Anna C. Y. Fan ◽  
Lisandra M. Gava ◽  
Carlos H. I. Ramos ◽  
Jason C. Young
Keyword(s):  
Heat Shock ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Size Exclusion ◽  
Mitochondrial Outer Membrane ◽  
Cross Linking ◽  
Wild Type ◽  
Oligomeric State ◽  
Mitochondrial Import ◽  
Import Receptor

The mitochondrial import receptor Tom70 (translocase of the mitochondrial outer membrane 70) interacts with chaperone–preprotein complexes through two domains: one that binds Hsp70 (heat-shock protein 70)/Hsc70 (heat-shock cognate 70) and Hsp90, and a second that binds preproteins. The oligomeric state of Tom70 has been controversial, with evidence for both monomeric and homodimeric forms. In the present paper, we report that the functional state of human Tom70 appears to be a monomer with mechanistic implications for its function in mitochondrial protein import. Based on analytical ultracentrifugation, cross-linking, size-exclusion chromatography and multi-angle light scattering, we found that the soluble cytosolic fragment of human Tom70 exists in equilibrium between monomer and dimer. A point mutation introduced at the predicted dimer interface increased the percentage of monomeric Tom70. Although chaperone docking to the mutant was the same as to the wild-type, the mutant was significantly more active in preprotein targeting. Cross-linking also demonstrated that the mutant formed stronger contacts with preprotein. However, cross-linking of full-length wild-type Tom70 on the mitochondrial membrane showed little evidence of homodimers. These results indicate that the Tom70 monomers are the functional form of the receptor, whereas the homodimers appear to be a minor population, and may represent an inactive state.

scholarly journals The ER protein Ema19 facilitates the degradation of non-imported mitochondrial precursor proteins

2021 ◽  
pp. mbc.E20-11-0748
Author(s):  
Janina Laborenz ◽  
Yury S. Bykov ◽  
Katharina Knöringer ◽  
Markus Räschle ◽  
Sabine Filker ◽  
...  
Keyword(s):  
Protein Import ◽  
Protein Targeting ◽  
Mitochondrial Protein ◽  
Integral Membrane Protein ◽  
Control Factor ◽  
Proteolytic Degradation ◽  
Molecular Function ◽  
Precursor Proteins ◽  
Biogenesis Of Mitochondria

For the biogenesis of mitochondria, hundreds of proteins need to be targeted from the cytosol into the various compartments of this organelle. The intramitochondrial targeting routes these proteins take to reach their respective location in the organelle are well understood. However, the early targeting processes, from cytosolic ribosomes to the membrane of the organelle, are still largely unknown. In this study, we present evidence that an integral membrane protein of the endoplasmic reticulum (ER), Ema19, plays a role in this process. Mutants lacking Ema19 show an increased stability of mitochondrial precursor proteins, indicating that Ema19 promotes the proteolytic degradation of non-productive precursors. The deletion of Ema19 improves the growth of respiration-deficient cells, suggesting that Ema19-mediated degradation can compete with productive protein import into mitochondria. Ema19 is the yeast representative of a conserved protein family. The human Ema19 homolog is known as sigma 2 receptor or TMEM97. Though its molecular function is not known, previous studies suggested a role of the sigma 2 receptor as a quality control factor in the ER, compatible with our observations about Ema19. More globally, our data provide an additional demonstration of the important role of the ER in mitochondrial protein targeting.

scholarly journals Dual role of the receptor Tom20 in specificity and efficiency of protein import into mitochondria

2010 ◽  
Vol 108 (1) ◽  
pp. 91-96 ◽  
Author(s):  
Hayashi Yamamoto ◽  
Nobuka Itoh ◽  
Shin Kawano ◽  
Yoh-ichi Yatsukawa ◽  
Takaki Momose ◽  
...  
Keyword(s):  
Essential Role ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Dual Role ◽  
Mitochondrial Protein Import ◽  
Targeting Signal ◽  
Terminal Element ◽  
Import Receptor

Mitochondria import most of their resident proteins from the cytosol, and the import receptor Tom20 of the outer-membrane translocator TOM40 complex plays an essential role in specificity of mitochondrial protein import. Here we analyzed the effects of Tom20 binding on NMR spectra of a long mitochondrial presequence and found that it contains two distinct Tom20-binding elements. In vitro import and cross-linking experiments revealed that, although the N-terminal Tom20-binding element is essential for targeting to mitochondria, the C-terminal element increases efficiency of protein import in the step prior to translocation across the inner membrane. Therefore Tom20 has a dual role in protein import into mitochondria: recognition of the targeting signal in the presequence and tethering the presequence to the TOM40 complex to increase import efficiency.

scholarly journals TOM20-mediated transfer of Bcl2 from ER to MAM and mitochondria upon induction of apoptosis

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Lisenn Lalier ◽  
Vincent Mignard ◽  
Marie-Pierre Joalland ◽  
Didier Lanoé ◽  
Pierre-François Cartron ◽  
...  
Keyword(s):  
Protein Import ◽  
Glioma Cells ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Localization ◽  
Antiapoptotic Protein ◽  
Mitochondrial Transfer ◽  
Small Domain ◽  
Induction Of Apoptosis ◽  
And Function

AbstractIn this work, we have explored the subcellular localization of Bcl2, a major antiapoptotic protein. In U251 glioma cells, we found that Bcl2 is localized mainly in the ER and is translocated to MAM and mitochondria upon induction of apoptosis; this mitochondrial transfer was not restricted to the demonstrator cell line, even if cell-specific modulations exist. We found that the Bcl2/mitochondria interaction is controlled by TOM20, a protein that belongs to the protein import machinery of the mitochondrial outer membrane. The expression of a small domain of interaction of TOM20 with Bcl2 potentiates its anti-apoptotic properties, which suggests that the Bcl2–TOM20 interaction is proapoptotic. The role of MAM and TOM20 in Bcl2 apoptotic mitochondrial localization and function has been confirmed in a yeast model in which the ER–mitochondria encounter structure (ERMES) complex (required for MAM stability in yeast) has been disrupted. Bcl2–TOM20 interaction is thus an additional player in the control of apoptosis.

scholarly journals Structural Basis of Presequence Recognition by the Mitochondrial Protein Import Receptor Tom20

Cell ◽  
2000 ◽  
Vol 100 (5) ◽  
pp. 551-560 ◽  
Author(s):  
Yoshito Abe ◽  
Toshihiro Shodai ◽  
Takanori Muto ◽  
Katsuyoshi Mihara ◽  
Hisayoshi Torii ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Structural Basis ◽  
Mitochondrial Protein Import ◽  
Import Receptor

scholarly journals Inactivation of the Neurospora crassa gene encoding the mitochondrial protein import receptor MOM19 by the technique of "sheltered RIP".

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 107-118 ◽  
Author(s):  
T A Harkness ◽  
R L Metzenberg ◽  
H Schneider ◽  
R Lill ◽  
W Neupert ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Target Gene ◽  
Protein Import ◽  
Selectable Marker ◽  
Mitochondrial Protein ◽  
Mutant Gene ◽  
Mitochondrial Protein Import ◽  
Gene Encoding ◽  
Precursor Proteins ◽  
Import Receptor

Abstract We have used a technique referred to as "sheltered RIP" (repeat induced point mutation) to create mutants of the mom-19 gene of Neurospora crassa, which encodes an import receptor for nuclear encoded mitochondrial precursor proteins. Sheltered RIP permits the isolation of a mutant gene in one nucleus, even if that gene is essential for the survival of the organism, by sheltering the nucleus carrying the mutant gene in a heterokaryon with an unaffected nucleus. Furthermore, the nucleus harboring the RIPed gene contains a selectable marker so that it is possible to shift nuclear ratios in the heterokaryons to a state in which the nucleus containing the RIPed gene predominates in cultures grown under selective conditions. This results in a condition where the target gene product should be present at very suboptimal levels and allows the study of the mutant phenotype. One allele of mom-19 generated by this method contains 44 transitions resulting in 18 amino acid substitutions. When the heterokaryon containing this allele was grown under conditions favoring the RIPed nucleus, no MOM19 protein was detectable in the mitochondria of the strain. Homokaryotic strains containing the RIPed allele exhibit a complex and extremely slow growth phenotype suggesting that the product of the mom-19 gene is important in N. crassa.

scholarly journals Phosphorylation of the mitochondrial triphosphate tunnel metalloenzyme TTM1 regulates programmed cell death in senescence

2020 ◽  
Author(s):  
Purva Karia ◽  
Keiko Yoshioka ◽  
Wolfgang Moeder
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Map Kinases ◽  
Mitochondrial Protein ◽  
Mitochondrial Outer Membrane ◽  
Mitogen Activated Protein ◽  
Animal Growth ◽  
Triphosphate Tunnel Metalloenzyme

ABSTRACTThe role of mitochondria in programmed cell death (PCD) during animal growth and development is well documented, but much less is known for plants. We previously showed that the Arabidopsis thaliana triphosphate tunnel metalloenzyme (TTM) proteins TTM1 and TTM2 are tail-anchored proteins that localize in the mitochondrial outer membrane and participate in PCD during senescence and immunity, respectively. Here, we show that TTM1 is specifically involved in senescence induced by abscisic acid (ABA). Moreover, phosphorylation of TTM1 by multiple mitogen-activated protein kinases (MAPKs) regulates its function and turnover. A combination of proteomics and in vitro kinase assays revealed three major phosphorylation sites of TTM1 (S10, S437, and S490), which are phosphorylated upon perception of senescence cues such as ABA and prolonged darkness. S437 is phosphorylated by the MAP kinases MPK3 and MPK4, and S437 phosphorylation is essential for TTM1 function in senescence. These MPKs, together with three additional MAP kinases (MPK1, MPK7, and MPK6), phosphorylate S10 and S490, marking TTM1 for protein turnover, which likely prevents uncontrolled cell death. Taken together, our results show that multiple MPKs regulate the function and turnover of the mitochondrial protein TTM1 during senescence-related PCD, revealing a novel link between mitochondria and PCD.SummaryEmail addresses: [email protected]

scholarly journals Role of the intermembrane-space domain of the preprotein receptor Tom22 in protein import into mitochondria.

1996 ◽  
Vol 16 (8) ◽  
pp. 4035-4042 ◽  
Author(s):  
D A Court ◽  
F E Nargang ◽  
H Steiner ◽  
R S Hodges ◽  
W Neupert ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Protein Translocation ◽  
Specific Binding ◽  
Mitochondrial Outer Membrane ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Terminal Domain ◽  
Tom Complex

Tom22 is an essential component of the protein translocation complex (Tom complex) of the mitochondrial outer membrane. The N-terminal domain of Tom22 functions as a preprotein receptor in cooperation with Tom20. The role of the C-terminal domain of Tom22, which is exposed to the intermembrane space (IMS), in its own assembly into the Tom complex and in the import of other preproteins was investigated. The C-terminal domain of Tom22 is not essential for the targeting and assembly of this protein, as constructs lacking part or all of the IMS domain became imported into mitochondria and assembled into the Tom complex. Mutant strains of Neurospora expressing the truncated Tom22 proteins were generated by a novel procedure. These mutants displayed wild-type growth rates, in contrast to cells lacking Tom22, which are not viable. The import of proteins into the outer membrane and the IMS of isolated mutant mitochondria was not affected. Some but not all preproteins destined for the matrix and inner membrane were imported less efficiently. The reduced import was not due to impaired interaction of presequences with their specific binding site on the trans side of the outer membrane. Rather, the IMS domain of Tom22 appears to slightly enhance the efficiency of the transfer of these preproteins to the import machinery of the inner membrane.

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