scholarly journals The translocator maintenance protein Tam41 is required for mitochondrial cardiolipin biosynthesis

2008 ◽  
Vol 183 (7) ◽  
pp. 1213-1221 ◽  
Author(s):  
Stephan Kutik ◽  
Michael Rissler ◽  
Xue Li Guan ◽  
Bernard Guiard ◽  
Guanghou Shui ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Respiratory Chain ◽  
Matrix Protein ◽  
Mitochondrial Protein ◽  
Pleiotropic Effects ◽  
Mitochondrial Matrix ◽  
Carrier Proteins ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

The mitochondrial inner membrane contains different translocator systems for the import of presequence-carrying proteins and carrier proteins. The translocator assembly and maintenance protein 41 (Tam41/mitochondrial matrix protein 37) was identified as a new member of the mitochondrial protein translocator systems by its role in maintaining the integrity and activity of the presequence translocase of the inner membrane (TIM23 complex). Here we demonstrate that the assembly of proteins imported by the carrier translocase, TIM22 complex, is even more strongly affected by the lack of Tam41. Moreover, respiratory chain supercomplexes and the inner membrane potential are impaired by lack of Tam41. The phenotype of Tam41-deficient mitochondria thus resembles that of mitochondria lacking cardiolipin. Indeed, we found that Tam41 is required for the biosynthesis of the dimeric phospholipid cardiolipin. The pleiotropic effects of the translocator maintenance protein on preprotein import and respiratory chain can be attributed to its role in biosynthesis of mitochondrial cardiolipin.

scholarly journals Characterization of Mmp37p, aSaccharomyces cerevisiaeMitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

2006 ◽  
Vol 17 (9) ◽  
pp. 4051-4062 ◽  
Author(s):  
Michelle R. Gallas ◽  
Mary K. Dienhart ◽  
Rosemary A. Stuart ◽  
Roy M. Long
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Close Proximity ◽  
The Matrix ◽  
Targeting Signal

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix.

scholarly journals YME1L controls the accumulation of respiratory chain subunits and is required for apoptotic resistance, cristae morphogenesis, and cell proliferation

2012 ◽  
Vol 23 (6) ◽  
pp. 1010-1023 ◽  
Author(s):  
Lukas Stiburek ◽  
Jana Cesnekova ◽  
Olga Kostkova ◽  
Daniela Fornuskova ◽  
Kamila Vinsova ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Membrane Protein ◽  
Respiratory Chain ◽  
Integral Membrane Protein ◽  
Intermembrane Space ◽  
Wild Type ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Human Orthologue ◽  
Excessive Accumulation

Mitochondrial ATPases associated with diverse cellular activities (AAA) proteases are involved in the quality control and processing of inner-membrane proteins. Here we investigate the cellular activities of YME1L, the human orthologue of the Yme1 subunit of the yeast i‑AAA complex, using stable short hairpin RNA knockdown and expression experiments. Human YME1L is shown to be an integral membrane protein that exposes its carboxy-terminus to the intermembrane space and exists in several complexes of 600–1100 kDa. The stable knockdown of YME1L in human embryonic kidney 293 cells led to impaired cell proliferation and apoptotic resistance, altered cristae morphology, diminished rotenone-sensitive respiration, and increased susceptibility to mitochondrial membrane protein carbonylation. Depletion of YME1L led to excessive accumulation of nonassembled respiratory chain subunits (Ndufb6, ND1, and Cox4) in the inner membrane. This was due to a lack of YME1L proteolytic activity, since the excessive accumulation of subunits was reversed by overexpression of wild-type YME1L but not a proteolytically inactive YME1L variant. Similarly, the expression of wild-type YME1L restored the lamellar cristae morphology of YME1L-deficient mitochondria. Our results demonstrate the importance of mitochondrial inner-membrane proteostasis to both mitochondrial and cellular function and integrity and reveal a novel role for YME1L in the proteolytic regulation of respiratory chain biogenesis.

Removal of a hydrophobic domain within the mature portion of a mitochondrial inner membrane protein causes its mislocalization to the matrix

1990 ◽  
Vol 10 (5) ◽  
pp. 1873-1881
Author(s):  
S M Glaser ◽  
B R Miller ◽  
M G Cumsky
Keyword(s):  
Amino Acids ◽  
Mitochondrial Matrix ◽  
Mature Protein ◽  
Wild Type ◽  
Inner Membrane ◽  
Hydrophobic Domain ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Inner Membrane Protein ◽  
Cognate Protein

We have examined the import and intramitochondrial localization of the precursor to yeast cytochrome c oxidase subunit Va, a protein of the mitochondrial inner membrane. The results of studies on the import of subunit Va derivatives carrying altered presequences suggest that the uptake of this protein is highly efficient. We found that a presequence of only 5 amino acids (Met-Leu-Ser-Leu-Arg) could direct the import and localization of subunit Va with wild-type efficiency, as judged by several different assays. We also found that subunit Va could be effectively targeted to the mitochondrial inner membrane with a heterologous presequence that failed to direct import of its cognate protein. The results presented here confirmed those of an earlier study and showed clearly that the information required to "sort" subunit Va to the inner membrane resides in the mature protein sequence, not within the presequence per se. We present additional evidence that the aforementioned sorting information is contained, at least in part, in a hydrophobic stretch of 22 amino acids residing within the C-terminal third of the protein. Removal of this domain caused subunit Va to be mislocalized to the mitochondrial matrix.

Abstract 332: Mitochondrial Inner-Membrane Potential Instability Promotes Sarcolemmal Electrical Instability after Ischemia-Reperfusion in Monolayers of Cardiac Myocytes

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Soroosh Solhjoo ◽  
Brian O’Rourke
Keyword(s):  
Membrane Potential ◽  
Cardiac Myocytes ◽  
Mitochondrial Function ◽  
Ischemia Reperfusion ◽  
Neonatal Rat ◽  
Partial Recovery ◽  
Mitochondrial Network ◽  
Electrical Excitability ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

Mitochondrial uncoupling due to oxidative stress can, through opening of sarcolemmal KATP channels, alter cellular electrical excitability, and it has been proposed that mitochondrial function is a major factor in arrhythmogenesis during ischemia-reperfusion. Here, we examine the effects of ischemia-reperfusion on mitochondrial inner membrane potential (ΔΨm) and corresponding changes in electrical excitability and wave propagation in monolayer cultures of neonatal rat ventricular myocytes. Changes in ΔΨm were observed using TMRM and changes in the sarcolemmal voltage were recorded with a 464-element photodiode array using di-4-ANEPPS. Ischemia was induced by covering the center part of the monolayer (D = 22 mm) with a coverslip (D = 15 mm). Cell contractions ceased after approximately 6 min of ischemia; however, electrical activity continued for 11.3 ± 4.2 min (N = 5). Amplitude and conduction velocity of the action potentials in the ischemic region decreased over the same time period. ΔΨm was lost in two phases: a reversible phase of partial depolarization, after 11.2 ± 1.3 min of ischemia, and a nonreversible phase, which happened after 30 ± 6 min of ischemia, during which the whole mitochondrial network of the myocyte became depolarized and the cells underwent contracture (N = 4). Reperfusion after the long ischemia resulted in only partial recovery and the observance of oscillations of ΔΨm in the mitochondrial network or rapid flickering of individual mitochondrial clusters and was associated with heterogeneous electrical recovery, and formation of wavelets and reentry (4/5 monolayers). In contrast, mitochondria fully recovered and reentry was rare (1/5 monolayers) for reperfusion after the short ischemia (10-12 min). 4’-chlorodiazepam, an inhibitor of inner membrane anion channels, stabilized mitochondrial function after the long ischemia, and prevented wavelets (5/5 monolayers) and reentry (4/5 monolayers). In conclusion, incomplete or unstable recovery of mitochondrial function after ischemia correlates with reentrant arrhythmias in monolayers of cardiac myocytes. Our findings suggest that stabilization of mitochondrial network dynamics is an important strategy for preventing ischemia/reperfusion-related arrhythmias.

scholarly journals The uptake of silicic acid by rat liver mitochondria

1978 ◽  
Vol 172 (3) ◽  
pp. 557-568 ◽  
Author(s):  
R N Johnson ◽  
B E Volcani
Keyword(s):  
Silicic Acid ◽  
Diffusion Mechanism ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Energy Status ◽  
Matrix Space ◽  
Inner Membrane ◽  
Simple Diffusion ◽  
Mitochondrial Inner Membrane

1. To gain insight into a putative role for mitochondria in silicon metabolism, mitochondrial uptake (by which it is meant the removal from the medium) of silicic acid [Si(OH)4] was studied under conditions minimizing SI(OH)4 polymerization. 2. Measurements of mitochondrial respiration and swelling indicated indirectly a significant uptake of Si(OH)4 as a weak acid, but this was not confirmed when 31Si(OH)4 was used as a tracer. 31Si(OH)4 occupied a mitochondrial volume similar to that of 3H2O and was relatively unaffected by mitochondrial energy status and by the pH gradient across the mitochondrial inner membrane. 3. Uptake was directly proportional to Si(OH)4 concentration in the range 0-3 mM. 4. The uptake consisted of two components: under all conditions examined, the greater quantity, amounting to 1-2nmol of Si(OH)4/mg of mitochondrial protein, was bound, a major portion of it external to the inner membrane, with the lesser quantity free within the matrix space. 5. Equilibration of 31Si(OH)4 between medium and matrix was a slow process, having a half-time of approx. 10 min at 22 degrees C. 6. Mersalyl and N-ethylmaleimide inhibited the uptake by preferentially lowering the amount of Si(OH)4 bound. Their action was somewhat variable, depending on the precise nature of the suspending medium, and suggesting that the bound material may represent polymerized forms of Si(OH)4. 7. It is concluded that Si(OH)4 may penetrate the mitochondrial inner membrane by a simple diffusion mechanism.

scholarly journals MAS6 encodes an essential inner membrane component of the yeast mitochondrial protein import pathway

1993 ◽  
Vol 122 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
JL Emtage ◽  
RE Jensen
Keyword(s):  
Protein Import ◽  
Early Stage ◽  
Osmotic Shock ◽  
Alkali Treatment ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

To identify new components that mediate mitochondrial protein import, we analyzed mas6, an import mutant in the yeast Saccharomyces cerevisiae. mas6 mutants are temperature sensitive for viability, and accumulate mitochondrial precursor proteins at the restrictive temperature. We show that mas6 does not correspond to any of the presently identified import mutants, and we find that mitochondria isolated from mas6 mutants are defective at an early stage of the mitochondrial protein import pathway. MAS6 encodes a 23-kD protein that contains several potential membrane spanning domains, and yeast strains disrupted for MAS6 are inviable at all temperatures and on all carbon sources. The Mas6 protein is located in the mitochondrial inner membrane and cannot be extracted from the membrane by alkali treatment. Antibodies to the Mas6 protein inhibit import into isolated mitochondria, but only when the outer membrane has been disrupted by osmotic shock. Mas6p therefore represents an essential import component located in the mitochondrial inner membrane.

scholarly journals SMS1, a high-copy suppressor of the yeast mas6 mutant, encodes an essential inner membrane protein required for mitochondrial protein import.

1994 ◽  
Vol 5 (5) ◽  
pp. 529-538 ◽  
Author(s):  
K R Ryan ◽  
M M Menold ◽  
S Garrett ◽  
R E Jensen
Keyword(s):  
Membrane Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Import ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Inner Membrane Protein ◽  
Membrane Spanning ◽  
Membrane Spanning Domains

MAS6 encodes an essential inner membrane protein required for mitochondrial protein import in the yeast Saccharomyces cerevisiae (Emtage and Jensen, 1993). To identify new inner membrane import components, we isolated a high-copy suppressor (SMS1) of the mas6-1 mutant. SMS1 encodes a 16.5-kDa protein that contains several potential membrane-spanning domains. The Sms1 protein is homologous to the carboxyl-terminal domain of the Mas6 protein. Like Mas6p, Sms1p is located in the mitochondrial inner membrane and is an essential protein. Depletion of Sms1p from cells causes defects in the import of several mitochondrial precursor proteins, suggesting that Sms1p is a new inner membrane import component. Our observations raise the possibility that Sms1p and Mas6p act together to translocate proteins across the inner membrane.

scholarly journals tRNAs and Proteins Are Imported into Mitochondria ofTrypanosoma brucei by Two Distinct Mechanisms

1999 ◽  
Vol 10 (8) ◽  
pp. 2547-2557 ◽  
Author(s):  
Christoph E. Nabholz ◽  
Elke K. Horn ◽  
André Schneider
Keyword(s):  
Membrane Potential ◽  
Trypanosoma Brucei ◽  
Matrix Protein ◽  
Mitochondrial Matrix ◽  
Trna Import ◽  
Hydrolysis Of

Import of tRNA into the mitochondrial matrix of Trypanosoma brucei was reconstituted in vitro. Efficient import required the hydrolysis of externally added ATP and was shown to be a carrier-mediated process depending on proteinaceous receptors on the surface of mitochondria. A partly synthetic tRNATyr as well as a physiological tRNALys were imported along the same pathway. Contrary to import of all matrix-localized proteins, tRNA import does not require a membrane potential. Furthermore, addition of an excess of import-competent tRNA had no effect on import of a mitochondrial matrix protein. In summary, these results show that tRNAs and proteins in T. brucei are imported by fundamentally different mechanisms.

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