scholarly journals Precursor Oxidation by Mia40 and Erv1 Promotes Vectorial Transport of Proteins into the Mitochondrial Intermembrane Space

2008 ◽  
Vol 19 (1) ◽  
pp. 226-236 ◽  
Author(s):  
Judith M. Müller ◽  
Dusanka Milenkovic ◽  
Bernard Guiard ◽  
Nikolaus Pfanner ◽  
Agnieszka Chacinska
Keyword(s):  
Experimental Evidence ◽  
Cysteine Residues ◽  
Intermembrane Space ◽  
Disulfide Formation ◽  
Precursor Proteins ◽  
Mitochondrial Intermembrane Space ◽  
Vectorial Transport ◽  
Tim Proteins

The mitochondrial intermembrane space contains chaperone complexes that guide hydrophobic precursor proteins through this aqueous compartment. The chaperones consist of hetero-oligomeric complexes of small Tim proteins with conserved cysteine residues. The precursors of small Tim proteins are synthesized in the cytosol. Import of the precursors requires the essential intermembrane space proteins Mia40 and Erv1 that were proposed to form a relay for disulfide formation in the precursor proteins. However, experimental evidence for a role of Mia40 and Erv1 in the oxidation of intermembrane space precursors has been lacking. We have established a system to directly monitor the oxidation of precursors during import into mitochondria and dissected distinct steps of the import process. Reduced precursors bind to Mia40 during translocation into mitochondria. Both Mia40 and Erv1 are required for formation of oxidized monomers of the precursors that subsequently assemble into oligomeric complexes. Whereas the reduced precursors can diffuse back into the cytosol, the oxidized precursors are retained in the intermembrane space. Thus, oxidation driven by Mia40 and Erv1 determines vectorial transport of the precursors into the mitochondrial intermembrane space.

Computational studies of the mitochondrial carrier family SLC25. Present status and future perspectives

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Andrea Pasquadibisceglie ◽  
Fabio Polticelli
Keyword(s):  
Transport Mechanism ◽  
Experimental Studies ◽  
Intermembrane Space ◽  
Mitochondrial Carrier ◽  
Mitochondrial Homeostasis ◽  
The Matrix ◽  
Mitochondrial Carrier Family ◽  
Mitochondrial Intermembrane Space ◽  
Computational Analyses

Abstract The members of the mitochondrial carrier family, also known as solute carrier family 25 (SLC25), are transmembrane proteins involved in the translocation of a plethora of small molecules between the mitochondrial intermembrane space and the matrix. These transporters are characterized by three homologous domains structure and a transport mechanism that involves the transition between different conformations. Mutations in regions critical for these transporters’ function often cause several diseases, given the crucial role of these proteins in the mitochondrial homeostasis. Experimental studies can be problematic in the case of membrane proteins, in particular concerning the characterization of the structure–function relationships. For this reason, computational methods are often applied in order to develop new hypotheses or to support/explain experimental evidence. Here the computational analyses carried out on the SLC25 members are reviewed, describing the main techniques used and the outcome in terms of improved knowledge of the transport mechanism. Potential future applications on this protein family of more recent and advanced in silico methods are also suggested.

scholarly journals Divergent Small Tim Homologues Are Associated with TbTim17 and Critical for the Biogenesis of TbTim17 Protein Complexes in Trypanosoma brucei

mSphere ◽  
2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Joseph T. Smith ◽  
Ujjal K. Singha ◽  
Smita Misra ◽  
Minu Chaudhuri
Keyword(s):  
Membrane Proteins ◽  
Trypanosoma Brucei ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Content Type ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Intermembrane Space ◽  
The Stability ◽  
Tim Proteins

ABSTRACT The small Tim proteins belong to a group of mitochondrial intermembrane space chaperones that aid in the import of mitochondrial inner membrane proteins with internal targeting signals. Trypanosoma brucei , the protozoan parasite that causes African trypanosomiasis, possesses multiple small Tim proteins that include homologues of T. brucei Tim9 (TbTim9) and Tim10 (TbTim10) and a unique small Tim that shares homology with both Tim8 and Tim13 (TbTim8/13). Here, we found that these three small TbTims are expressed as soluble mitochondrial intermembrane space proteins. Coimmunoprecipitation and mass spectrometry analysis showed that the small TbTims stably associated with each other and with TbTim17, the major component of the mitochondrial inner membrane translocase in T. brucei . Yeast two-hybrid analysis indicated direct interactions among the small TbTims; however, their interaction patterns appeared to be different from those of their counterparts in yeast and humans. Knockdown of the small TbTims reduced cell growth and decreased the steady-state level of TbTim17 and T. brucei ADP/ATP carrier (TbAAC), two polytopic mitochondrial inner membrane proteins. Knockdown of small TbTims also reduced the matured complexes of TbTim17 in mitochondria. Depletion of any of the small TbTims reduced TbTim17 import moderately but greatly hampered the stability of the TbTim17 complexes in T. brucei . Altogether, our results revealed that TbTim9, TbTim10, and TbTim8/13 interact with each other, associate with TbTim17, and play a crucial role in the integrity and maintenance of the levels of TbTim17 complexes. IMPORTANCE Trypanosoma brucei is the causative agent of African sleeping sickness. The parasite’s mitochondrion represents a useful source for potential chemotherapeutic targets. Similarly to yeast and humans, mitochondrial functions depend on the import of proteins that are encoded in the nucleus and made in the cytosol. Even though the machinery involved in this mitochondrial protein import process is becoming clearer in T. brucei , a comprehensive picture of protein complex composition and function is still lacking. In this study, we characterized three T. brucei small Tim proteins, TbTim9, TbTim10, and TbTim8/13. Although the parasite does not have the classical TIM22 complex that imports mitochondrial inner membrane proteins containing internal targeting signals in yeast or humans, we found that these small TbTims associate with TbTim17, the major subunit of the TbTIM complex in T. brucei , and play an essential role in the stability of the TbTim17 complexes. Therefore, these divergent proteins are critical for mitochondrial protein biogenesis in T. brucei .

scholarly journals Cysteine residues in mitochondrial intermembrane space proteins: more than just import

2018 ◽  
Vol 176 (4) ◽  
pp. 514-531 ◽  
Author(s):  
Markus Habich ◽  
Silja Lucia Salscheider ◽  
Jan Riemer
Keyword(s):  
Cysteine Residues ◽  
Intermembrane Space ◽  
Mitochondrial Intermembrane Space

Oxidative folding competes with mitochondrial import of the small Tim proteins

2008 ◽  
Vol 411 (1) ◽  
pp. 115-122 ◽  
Author(s):  
Bruce Morgan ◽  
Hui Lu
Keyword(s):  
Disulfide Bonds ◽  
Intermembrane Space ◽  
Mitochondrial Import ◽  
Oxidative Folding ◽  
Mutant Proteins ◽  
Standard Redox Potential ◽  
Mitochondrial Intermembrane Space ◽  
Tim Proteins

All small Tim proteins of the mitochondrial intermembrane space contain two conserved CX3C motifs, which form two intramolecular disulfide bonds essential for function, but only the cysteine-reduced, but not oxidized, proteins can be imported into mitochondria. We have shown that Tim10 can be oxidized by glutathione under cytosolic concentrations. However, it was unknown whether oxidative folding of other small Tims can occur under similar conditions and whether oxidative folding competes kinetically with mitochondrial import. In the present study, the effect of glutathione on the cysteine-redox state of Tim9 was investigated, and the standard redox potential of Tim9 was determined to be approx. −0.31 V at pH 7.4 and 25 °C with both the wild-type and Tim9F43W mutant proteins, using reverse-phase HPLC and fluorescence approaches. The results show that reduced Tim9 can be oxidized by glutathione under cytosolic concentrations. Next, we studied the rate of mitochondrial import and oxidative folding of Tim9 under identical conditions. The rate of import was approx. 3-fold slower than that of oxidative folding of Tim9, resulting in approx. 20% of the precursor protein being imported into an excess amount of mitochondria. A similar correlation between import and oxidative folding was obtained for Tim10. Therefore we conclude that oxidative folding and mitochondrial import are kinetically competitive processes. The efficiency of mitochondrial import of the small Tim proteins is controlled, at least partially in vitro, by the rate of oxidative folding, suggesting that a cofactor is required to stabilize the cysteine residues of the precursors from oxidation in vivo.

scholarly journals IGF2R-initiated proton rechanneling dictates an anti-inflammatory property in macrophages

2020 ◽  
Vol 6 (48) ◽  
pp. eabb7389
Author(s):  
Xuefeng Wang ◽  
Liangyu Lin ◽  
Bin Lan ◽  
Yu Wang ◽  
Liming Du ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Growth Factor ◽  
Low Dose ◽  
High Dose ◽  
Intermembrane Space ◽  
Mitochondrial Intermembrane Space ◽  
Anti Inflammatory ◽  
Inflammatory Macrophages ◽  
Inflammatory Phenotypes

Metabolic traits of macrophages can be rewired by insulin-like growth factor 2 (IGF2); however, how IGF2 modulates macrophage cellular dynamics and functionality remains unclear. We demonstrate that IGF2 exhibits dual and opposing roles in controlling inflammatory phenotypes in macrophages by regulating glucose metabolism, relying on the dominant activation of the IGF2 receptor (IGF2R) by low-dose IGF2 (L-IGF2) and IGF1R by high-dose IGF2. IGF2R activation leads to proton rechanneling to the mitochondrial intermembrane space and enables sustained oxidative phosphorylation. Mechanistically, L-IGF2 induces nucleus translocation of IGF2R that promotes Dnmt3a-mediated DNA methylation by activating GSK3α/β and subsequently impairs expression of vacuolar-type H+-ATPase (v-ATPase). This sequestrated assembly of v-ATPase inhibits the channeling of protons to lysosomes and leads to their rechanneling to mitochondria. An IGF2R-specific IGF2 mutant induces only the anti-inflammatory response and inhibits colitis progression. Together, our findings highlight a previously unidentified role of IGF2R activation in dictating anti-inflammatory macrophages.

Protein import by the mitochondrial disulfide relay in higher eukaryotes

2020 ◽  
Vol 401 (6-7) ◽  
pp. 749-763 ◽  
Author(s):  
Yannik Finger ◽  
Jan Riemer
Keyword(s):  
Liver Regeneration ◽  
Respiratory Chain ◽  
Protein Import ◽  
Intermembrane Space ◽  
Sulfhydryl Oxidase ◽  
Disulfide Formation ◽  
Physiological Relevance ◽  
Mitochondrial Intermembrane Space ◽  
Higher Eukaryotes ◽  
Import System

AbstractThe proteome of the mitochondrial intermembrane space (IMS) contains more than 100 proteins, all of which are synthesized on cytosolic ribosomes and consequently need to be imported by dedicated machineries. The mitochondrial disulfide relay is the major import machinery for soluble proteins in the IMS. Its major component, the oxidoreductase MIA40, interacts with incoming substrates, retains them in the IMS, and oxidatively folds them. After this reaction, MIA40 is reoxidized by the sulfhydryl oxidase augmenter of liver regeneration, which couples disulfide formation by this machinery to the activity of the respiratory chain. In this review, we will discuss the import of IMS proteins with a focus on recent findings showing the diversity of disulfide relay substrates, describing the cytosolic control of this import system and highlighting the physiological relevance of the disulfide relay machinery in higher eukaryotes.

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