scholarly journals Mutational Analysis of the Saccharomyces cerevisiae Cytochrome c Oxidase Assembly Protein Cox11p

2006 ◽  
Vol 5 (3) ◽  
pp. 568-578 ◽  
Author(s):  
Graham S. Banting ◽  
D. Moira Glerum
Keyword(s):  
Hydrogen Peroxide ◽  
Cytochrome Oxidase ◽  
Solution Structure ◽  
Sinorhizobium Meliloti ◽  
Mutational Analysis ◽  
Intermembrane Space ◽  
Copper Binding ◽  
Inner Mitochondrial Membrane ◽  
The Matrix

ABSTRACT Cox11p is an integral protein of the inner mitochondrial membrane that is essential for cytochrome c oxidase assembly. The bulk of the protein is located in the intermembrane space and displays high levels of evolutionary conservation. We have analyzed a collection of site-directed and random cox11 mutants in an effort to further define essential portions of the molecule. Of the alleles studied, more than half had no apparent effect on Cox11p function. Among the respiration deficiency-encoding alleles, we identified three distinct phenotypes, which included a set of mutants with a misassembled or partially assembled cytochrome oxidase, as indicated by a blue-shifted cytochrome aa 3 peak. In addition to the shifted spectral signal, these mutants also display a specific reduction in the levels of subunit 1 (Cox1p). Two of these mutations are likely to occlude a surface pocket behind the copper-binding domain in Cox11p, based on analogy with the Sinorhizobium meliloti Cox11 solution structure, thereby suggesting that this pocket is crucial for Cox11p function. Sequential deletions of the matrix portion of Cox11p suggest that this domain is not functional beyond the residues involved in mitochondrial targeting and membrane insertion. In addition, our studies indicate that Δcox11, like Δsco1, displays a specific hypersensitivity to hydrogen peroxide. Our studies provide the first evidence at the level of the cytochrome oxidase holoenzyme that Cox1p is the in vivo target for Cox11p and suggest that Cox11p may also have a role in the response to hydrogen peroxide exposure.

scholarly journals Protein sorting between mitochondrial membranes specified by position of the stop-transfer domain.

1988 ◽  
Vol 106 (5) ◽  
pp. 1499-1505 ◽  
Author(s):  
M Nguyen ◽  
A W Bell ◽  
G C Shore
Keyword(s):  
G Protein ◽  
Simple Extension ◽  
Intermembrane Space ◽  
Mitochondrial Membranes ◽  
Inner Mitochondrial Membrane ◽  
The Matrix ◽  
Targeting Signal ◽  
Vesicular Stomatitis ◽  
Matrix Precursor ◽  
Identical Fashion

Recently, we fused a matrix-targeting signal to a large fragment of vesicular stomatitis virus G protein, which contains near its COOH-terminus a well-characterized endoplasmic reticulum (ER) stop-transfer sequence; the hybrid G protein was sorted to the inner mitochondrial membrane (Nguyen, M., and G. C. Shore. 1987. J. Biol. Chem. 262:3929-3931). Here, we show that the 19 amino acid G stop-transfer domain functions in an identical fashion when inserted toward the COOH-terminus of an otherwise normal matrix precursor protein, pre-ornithine carbamyl transferase; after import, the mutant protein was found anchored in the inner membrane via the stop-transfer sequence, with its NH2 terminus facing the matrix and its short COOH-terminal tail located in the intermembrane space. However, when the G stop-transfer sequence was placed near the NH2 terminus, the protein was inserted into the outer membrane, in the reverse orientation (NH2 terminus facing out, with a large COOH-terminal fragment located in the intermembrane space). These observations for mitochondrial topogenesis can be explained by a simple extension of existing models for ER sorting.

Abstract P334: Biophysical Properties Of A Novel Mitochondrial Large Ubiquitous Non-selective Amiloride Sensitive (luna) Current

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Enrique Balderas-Angeles ◽  
Thirupura Shankar ◽  
Anthony Balynas ◽  
Xue Yin ◽  
Dipayan Chaudhuri
Keyword(s):  
Ion Channels ◽  
Divalent Cations ◽  
Pressure Overload ◽  
Atp Synthesis ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Patch Clamp Technique ◽  
Transport Chain ◽  
The Matrix ◽  
Established Cell

Inner mitochondrial membrane (IMM) ion channels and transporters account for communication of the matrix with the intermembrane space (IMS) and the cytosol. Transport of solutes and ions is keep under strict regulation mainly because small changes in solute concentrations could generate changes in mitochondrial volume or membrane potential (ΔΨ m ), interrupting ATP synthesis and leading to mitochondrial damage. The list of recently discovered mitochondrial ion channels has been growing in the past decades. In this work, using the patch-clamp technique we observed the activity of a novel mitochondrial current, named here LUNA current, in mitoplasts (IMM striped of outer membrane) from mouse liver, spleen, brain and heart, as well as established cell lines. LUNA is a novel non-selective cation current (K + >Na + >NMDG + >H + ) active at depolarized membrane potentials. The basal activity of whole-mitoplast LUNA currents from wild type mice hearts changed from 445±106 pA/pF to 1232±287 pA/pF upon chelation of external divalent cations (Ca 2+ and Mg 2+ ). Moreover, the activity of LUNA is independent of the mitochondrial Ca 2+ uniporter and of the non-selective reactive oxygen species modulator channel (ROMO1). In the heart, the activity of LUNA was enhanced in both the Tfam -KO mice, which have impaired electron transport chain (ETC) activity and are a model for mitochondrial cardiomyopathies, and mice with cardiac pressure overload due to transverse aortic constriction (TAC) compared to sham-operated hearts (729±197; n=7 vs 283±137 pA/pF). LUNA current is reversibly inhibited by amiloride with no sensitivity to the vast majority of common K + , Na + and Ca 2+ channels and ETC inhibitors. The molecular identity of mitochondrial LUNA current remains to be determined.

scholarly journals Role of cytochrome c heme lyase in mitochondrial import and accumulation of cytochrome c in Saccharomyces cerevisiae.

1991 ◽  
Vol 11 (11) ◽  
pp. 5487-5496 ◽  
Author(s):  
M E Dumont ◽  
T S Cardillo ◽  
M K Hayes ◽  
F Sherman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Mitochondrial Membrane ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Yeast Saccharomyces Cerevisiae ◽  
Apocytochrome C ◽  
Cytochrome C Heme Lyase

Heme is covalently attached to cytochrome c by the enzyme cytochrome c heme lyase. To test whether heme attachment is required for import of cytochrome c into mitochondria in vivo, antibodies to cytochrome c have been used to assay the distributions of apo- and holocytochromes c in the cytoplasm and mitochondria from various strains of the yeast Saccharomyces cerevisiae. Strains lacking heme lyase accumulate apocytochrome c in the cytoplasm. Similar cytoplasmic accumulation is observed for an altered apocytochrome c in which serine residues were substituted for the two cysteine residues that normally serve as sites of heme attachment, even in the presence of normal levels of heme lyase. However, detectable amounts of this altered apocytochrome c are also found inside mitochondria. The level of internalized altered apocytochrome c is decreased in a strain that completely lacks heme lyase and is greatly increased in a strain that overexpresses heme lyase. Antibodies recognizing heme lyase were used to demonstrate that the enzyme is found on the outer surface of the inner mitochondrial membrane and is not enriched at sites of contact between the inner and outer mitochondrial membranes. These results suggest that apocytochrome c is transported across the outer mitochondrial membrane by a freely reversible process, binds to heme lyase in the intermembrane space, and is then trapped inside mitochondria by an irreversible conversion to holocytochrome c accompanied by folding to the native conformation. Altered apocytochrome c lacking the ability to have heme covalently attached accumulates in mitochondria only to the extent that it remains bound to heme lyase.

scholarly journals The mitochondrial carrier pathway transports non-canonical substrates with an odd number of transmembrane segments

BMC Biology ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Heike Rampelt ◽  
Iva Sucec ◽  
Beate Bersch ◽  
Patrick Horten ◽  
Inge Perschil ◽  
...  
Keyword(s):  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Inner Membrane ◽  
Mitochondrial Carrier ◽  
Transmembrane Segments ◽  
Mitochondrial Inner Membrane ◽  
N Terminus ◽  
The Matrix ◽  
Mitochondrial Carrier Family ◽  
Mitochondrial Intermembrane Space

Abstract Background The mitochondrial pyruvate carrier (MPC) plays a central role in energy metabolism by transporting pyruvate across the inner mitochondrial membrane. Its heterodimeric composition and homology to SWEET and semiSWEET transporters set the MPC apart from the canonical mitochondrial carrier family (named MCF or SLC25). The import of the canonical carriers is mediated by the carrier translocase of the inner membrane (TIM22) pathway and is dependent on their structure, which features an even number of transmembrane segments and both termini in the intermembrane space. The import pathway of MPC proteins has not been elucidated. The odd number of transmembrane segments and positioning of the N-terminus in the matrix argues against an import via the TIM22 carrier pathway but favors an import via the flexible presequence pathway. Results Here, we systematically analyzed the import pathways of Mpc2 and Mpc3 and report that, contrary to an expected import via the flexible presequence pathway, yeast MPC proteins with an odd number of transmembrane segments and matrix-exposed N-terminus are imported by the carrier pathway, using the receptor Tom70, small TIM chaperones, and the TIM22 complex. The TIM9·10 complex chaperones MPC proteins through the mitochondrial intermembrane space using conserved hydrophobic motifs that are also required for the interaction with canonical carrier proteins. Conclusions The carrier pathway can import paired and non-paired transmembrane helices and translocate N-termini to either side of the mitochondrial inner membrane, revealing an unexpected versatility of the mitochondrial import pathway for non-cleavable inner membrane proteins.

scholarly journals A New Function in Translocation for the Mitochondrial i-AAA Protease Yme1: Import of Polynucleotide Phosphorylase into the Intermembrane Space

2006 ◽  
Vol 26 (22) ◽  
pp. 8488-8497 ◽  
Author(s):  
Robert N. Rainey ◽  
Jenny D. Glavin ◽  
Hsiao-Wen Chen ◽  
Samuel W. French ◽  
Michael A. Teitell ◽  
...  
Keyword(s):  
Protein Translocation ◽  
Rna Degradation ◽  
Mechanistic Study ◽  
Intermembrane Space ◽  
Polynucleotide Phosphorylase ◽  
Cellular Effects ◽  
The Matrix ◽  
Mitochondrial Intermembrane Space ◽  
Processing Peptidase

ABSTRACT Polynucleotide phosphorylase (PNPase) is an exoribonuclease and poly(A) polymerase postulated to function in the cytosol and mitochondrial matrix. Prior overexpression studies resulted in PNPase localization to both the cytosol and mitochondria, concurrent with cytosolic RNA degradation and pleiotropic cellular effects, including growth inhibition and apoptosis, that may not reflect a physiologic role for endogenous PNPase. We therefore conducted a mechanistic study of PNPase biogenesis in the mitochondrion. Interestingly, PNPase is localized to the intermembrane space by a novel import pathway. PNPase has a typical N-terminal targeting sequence that is cleaved by the matrix processing peptidase when PNPase engaged the TIM23 translocon at the inner membrane. The i-AAA protease Yme1 mediated translocation of PNPase into the intermembrane space but did not degrade PNPase. In a yeast strain deleted for Yme1 and expressing PNPase, nonimported PNPase accumulated in the cytosol, confirming an in vivo role for Yme1 in PNPase maturation. PNPase localization to the mitochondrial intermembrane space suggests a unique role distinct from its highly conserved function in RNA processing in chloroplasts and bacteria. Furthermore, Yme1 has a new function in protein translocation, indicating that the intermembrane space harbors diverse pathways for protein translocation.

scholarly journals Localization of dynein light chains 1 and 2 and their pro-apoptotic ligands

2004 ◽  
Vol 377 (3) ◽  
pp. 597-605 ◽  
Author(s):  
Catherine L. DAY ◽  
Hamsa PUTHALAKATH ◽  
Gretchen SKEA ◽  
Andreas STRASSER ◽  
Igor BARSUKOV ◽  
...  
Keyword(s):  
Cell Death ◽  
Solution Structure ◽  
Mutational Analysis ◽  
Protein Structures ◽  
Myosin V ◽  
Dimensional Solution ◽  
Binding Characteristics ◽  
Motor Complex

The dynein and myosin V motor complexes are multi-protein structures that function to transport molecules and organelles within the cell. DLC (dynein light-chain) proteins, found as components of both dynein and myosin V motor complexes, connect the complexes to their cargoes. One of the roles of these motor complexes is to selectively sequester the pro-apoptotic ‘BH3-only’ (Bcl-2 homology 3-only) proteins, Bim (Bcl-2-interacting mediator of cell death) and Bmf (Bcl-2-modifying factor), and so regulate their cell death-inducing function. In vivo DLC2 is found exclusively as a component of the myosin V motor complex and Bmf binds DLC2 selectively. On the other hand, Bim interacts with DLC1 (LC8), an integral component of the dynein motor complex. The two DLCs share 93% sequence identity yet show unambiguous in vivo specificity for their respective BH3-only ligands. To investigate this specificity the three-dimensional solution structure of DLC2 was elucidated using NMR spectroscopy. In vitro structural and mutagenesis studies show that Bmf and Bim have identical binding characteristics to recombinant DLC2 or DLC1. Thus the selectivity shown by Bmf and Bim for binding DLC1 or DLC2, respectively, does not reside in their DLC-binding domains. Remarkably, mutational analysis of DLC1 and DLC2 indicates that a single surface residue (residue 41) determines the specific localization of DLCs with their respective motor complexes. These results suggest a molecular mechanism for the specific compartmentalization of DLCs and their pro-apoptotic cargoes and implicate other protein(s) in defining the specificity between the cargoes and the DLC proteins.

scholarly journals Residues of Tim44 Involved in both Association with the Translocon of the Inner Mitochondrial Membrane and Regulation of Mitochondrial Hsp70 Tethering

2008 ◽  
Vol 28 (13) ◽  
pp. 4424-4433 ◽  
Author(s):  
Dirk Schiller ◽  
Yu Chin Cheng ◽  
Qinglian Liu ◽  
William Walter ◽  
Elizabeth A. Craig
Keyword(s):  
Amino Acid ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Inner Mitochondrial Membrane ◽  
The Matrix ◽  
Mitochondrial Hsp70 ◽  
Amino Acid Segment

ABSTRACT Translocation of proteins from the cytosol across the mitochondrial inner membrane is driven by the action of the import motor, which is associated with the translocon on the matrix side of the membrane. It is well established that an essential peripheral membrane protein, Tim44, tethers mitochondrial Hsp70 (mtHsp70), the core of the import motor, to the translocon. This Tim44-mtHsp70 interaction, which can be recapitulated in vitro, is destabilized by binding of mtHsp70 to a substrate polypeptide. Here we report that the N-terminal 167-amino-acid segment of mature Tim44 is sufficient for both interaction with mtHsp70 and destabilization of a Tim44-mtHsp70 complex caused by client protein binding. Amino acid alterations within a 30-amino-acid segment affected both the release of mtHsp70 upon peptide binding and the interaction of Tim44 with the translocon. Our results support the idea that Tim44 plays multiple roles in mitochondrial protein import by recruiting Ssc1 and its J protein cochaperone to the translocon and coordinating their interactions to promote efficient protein translocation in vivo.

Thiol switches in mitochondria: operation and physiological relevance

2015 ◽  
Vol 396 (5) ◽  
pp. 465-482 ◽  
Author(s):  
Jan Riemer ◽  
Markus Schwarzländer ◽  
Marcus Conrad ◽  
Johannes M. Herrmann
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Redox Conditions ◽  
Cysteine Residues ◽  
Mitochondrial Enzymes ◽  
Intermembrane Space ◽  
Oxygen Species ◽  
Redox Systems ◽  
Physiological Relevance ◽  
The Matrix

Abstract Mitochondria are a major source of reactive oxygen species (ROS) in the cell, particularly of superoxide and hydrogen peroxide. A number of dedicated enzymes regulate the conversion and consumption of superoxide and hydrogen peroxide in the intermembrane space and the matrix of mitochondria. Nevertheless, hydrogen peroxide can also interact with many other mitochondrial enzymes, particularly those with reactive cysteine residues, modulating their reactivity in accordance with changes in redox conditions. In this review we will describe the general redox systems in mitochondria of animals, fungi and plants and discuss potential target proteins that were proposed to contain regulatory thiol switches.

scholarly journals Membrane translocation of mitochondrially coded Cox2p: distinct requirements for export of N and C termini and dependence on the conserved protein Oxa1p.

1997 ◽  
Vol 8 (8) ◽  
pp. 1449-1460 ◽  
Author(s):  
S He ◽  
T D Fox
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitochondrial Gene ◽  
Leader Peptide ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
C Terminus ◽  
The Matrix ◽  
Inner Membrane Protein ◽  
Export System

To study in vivo the export of mitochondrially synthesized protein from the matrix to the intermembrane space, we have fused a synthetic mitochondrial gene, ARG8m, to the Saccharomyces cerevisiae COX2 gene in mitochondrial DNA. The Arg8mp moiety was translocated through the inner membrane when fused to the Cox2p C terminus by a mechanism dependent on topogenic information at least partially contained within the exported Cox2p C-terminal tail. The pre-Cox2p leader peptide did not signal translocation. Export of the Cox2p C-terminal tail, but not the N-terminal tail, was dependent on the inner membrane potential. The mitochondrial export system does not closely resemble the bacterial Sec translocase. However, normal translocation of both exported domains of Cox2p was defective in cells lacking the widely conserved inner membrane protein Oxa1p.

nde1 deletion improves mitochondrial DNA maintenance in Saccharomyces cerevisiae coenzyme Q mutants

2013 ◽  
Vol 449 (3) ◽  
pp. 595-603 ◽  
Author(s):  
Fernando Gomes ◽  
Erich B. Tahara ◽  
Cleverson Busso ◽  
Alicia J. Kowaltowski ◽  
Mario H. Barros
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitochondrial Dna ◽  
Coenzyme Q ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Yeast Strains ◽  
The Matrix ◽  
Nadh Dehydrogenases ◽  
Genetically Manipulated ◽  
Dna Maintenance

Saccharomyces cerevisiae has three distinct inner mitochondrial membrane NADH dehydrogenases mediating the transfer of electrons from NADH to CoQ (coenzyme Q): Nde1p, Nde2p and Ndi1p. The active site of Ndi1p faces the matrix side, whereas the enzymatic activities of Nde1p and Nde2p are restricted to the intermembrane space side, where they are responsible for cytosolic NADH oxidation. In the present study we genetically manipulated yeast strains in order to alter the redox state of CoQ and NADH dehydrogenases to evaluate the consequences on mtDNA (mitochondrial DNA) maintenance. Interestingly, nde1 deletion was protective for mtDNA in strains defective in CoQ function. Additionally, the absence of functional Nde1p promoted a decrease in the rate of H2O2 release in isolated mitochondria from different yeast strains. On the other hand, overexpression of the predominant NADH dehydrogenase NDE1 elevated the rate of mtDNA loss and was toxic to coq10 and coq4 mutants. Increased CoQ synthesis through COQ8 overexpression also demonstrated that there is a correlation between CoQ respiratory function and mtDNA loss: supraphysiological CoQ levels were protective against mtDNA loss in the presence of oxidative imbalance generated by Nde1p excess or exogenous H2O2. Altogether, our results indicate that impairment in the oxidation of cytosolic NADH by Nde1p is deleterious towards mitochondrial biogenesis due to an increase in reactive oxygen species release.

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