3d Structure Of Periodic Cubic-Phase Inner Membranes In Mitochondria of Chaos Carolinensis

1998 ◽  
Vol 4 (S2) ◽  
pp. 432-433
Author(s):  
Y. Deng ◽  
M. Mieczkowski ◽  
M. Marko ◽  
K. Buttle ◽  
B.K. Rath ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Detailed Analysis ◽  
Thin Section ◽  
3D Structure ◽  
Design Feature ◽  
Cubic Phase ◽  
Electron Microscopic ◽  
Inner Membrane ◽  
Cubic Surfaces ◽  
Mitochondrial Inner Membrane

The mitochondrial inner membrane contains the machinery of oxidative phosphorylation. This membrane has invaginations called cristae which vary widely in shape between organisms and between tissues in the same organism. Electron microscopic tomography indicates that, despite this pleiomorphism, there is a common design feature, namely, the cristal membranes connect to each other and to the periphery of the inner membrane by tubular regions 30-40 nm in diameter. This finding has important implications for the internal diffusion of ions, metabolites and macromolecules within mitochondria.In some types of mitochondria, the cristae exhibit periodicity.1 In the case of the amoeba Chaos carolinensis, detailed analysis and modeling of thin-section images of mitochondria in starved cells indicate that the highly curved cristae correspond to periodic cubic surfaces. We are undertaking electron microscopic tomographic and crystallographic approaches to more thoroughly characterize these membrane phases and, in particular, establish the continuity of the internal compartments which they define.

Electron Microscopic Tomography of Cellular Organelles: Chemical Fixation Vs. Cryo-Substitution of Rat-Liver Mitochondria

1998 ◽  
Vol 4 (S2) ◽  
pp. 430-431
Author(s):  
C.A. Mannella ◽  
K. Buttle ◽  
K. Tessitore ◽  
B.K. Rath ◽  
C. Hsieh ◽  
...  
Keyword(s):  
Rat Liver ◽  
3D Structure ◽  
Design Feature ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electron Microscopic ◽  
Inner Membrane ◽  
Low Contrast ◽  
Mitochondrial Inner Membrane ◽  
Cellular Organelles

Electron microscopic tomography is proving to be a valuable tool for investigating the 3D structure and organization of cellular organelles. Important progress is being made in the application of the technique to frozen-hydrated material, but it is likely that success with thick specimens will be limited by the low contrast and beam sensitivity of naked biological material. Thus, optimizing procedures for fixing, embedding, staining, and selectively labelling cells for 3D electron microscopy remains a priority.Tomography of chemically fixed and plastic-embedded rat-liver tissue and isolated mitochondria has shown that the cristae (the invaginations of the mitochondrial inner membrane) are pleiomorphic and connected to each other and to the surface of the inner membrane by tubular regions 30-40 nm in diameter. This basic design feature has important implications for the microcompartmentation of ions and molecules within this organelle.

scholarly journals Mapping of the Saccharomyces cerevisiae Oxa1-Mitochondrial Ribosome Interface and Identification of MrpL40, a Ribosomal Protein in Close Proximity to Oxa1 and Critical for Oxidative Phosphorylation Complex Assembly

2009 ◽  
Vol 8 (11) ◽  
pp. 1792-1802 ◽  
Author(s):  
Lixia Jia ◽  
Jasvinder Kaur ◽  
Rosemary A. Stuart
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Oxidative Phosphorylation ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Close Association ◽  
Ribosomal Subunit ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Ribosome ◽  
Encoded Proteins

ABSTRACT The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is also provided. MrpL40 shares sequence features with the bacterial ribosomal protein L24, which like Mrp20/L23 is known to be located adjacent to the ribosomal polypeptide exit site. We propose therefore that MrpL40 represents the Saccharomyces cerevisiae L24 homolog. MrpL40, like many mitochondrial ribosomal proteins, contains a C-terminal extension region that bears no similarity to the bacterial counterpart. We show that this C-terminal mitochondria-specific region is important for MrpL40's ability to support the synthesis of the correct complement of mitochondrially encoded proteins and their subsequent assembly into oxidative phosphorylation complexes.

scholarly journals Cardiolipin defines the interactome of the major ADP/ATP carrier protein of the mitochondrial inner membrane

2008 ◽  
Vol 182 (5) ◽  
pp. 937-950 ◽  
Author(s):  
Steven M. Claypool ◽  
Yavuz Oktay ◽  
Pinmanee Boontheung ◽  
Joseph A. Loo ◽  
Carla M. Koehler
Keyword(s):  
Oxidative Phosphorylation ◽  
Respiratory Function ◽  
Protein Complexes ◽  
Progressive External Ophthalmoplegia ◽  
Carrier Protein ◽  
Affinity Tag ◽  
Inner Membrane ◽  
Mitochondrial Carrier ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Carrier Family

Defined mutations in the mitochondrial ADP/ATP carrier (AAC) are associated with certain types of progressive external ophthalmoplegia. AAC is required for oxidative phosphorylation (OXPHOS), and dysregulation of AAC has been implicated in apoptosis. Little is known about the AAC interactome, aside from a known requirement for the phospholipid cardiolipin (CL) and that it is thought to function as a homodimer. Using a newly developed dual affinity tag, we demonstrate that yeast AAC2 physically participates in several protein complexes of distinct size and composition. The respiratory supercomplex and several smaller AAC2-containing complexes, including other members of the mitochondrial carrier family, are identified here. In the absence of CL, most of the defined interactions are destabilized or undetectable. The absence of CL and/or AAC2 results in distinct yet additive alterations in respiratory supercomplex structure and respiratory function. Thus, a single lipid can significantly alter the functional interactome of an individual protein.

scholarly journals Cryo-EM structures of S-OPA1 reveal its interactions with membrane and changes upon nucleotide binding

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Danyang Zhang ◽  
Yan Zhang ◽  
Jun Ma ◽  
Chunmei Zhu ◽  
Tongxin Niu ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Bound States ◽  
Proteolytic Processing ◽  
Power Stroke ◽  
Electron Microscopic ◽  
Inner Membrane ◽  
Hydrophobic Residues ◽  
Physiological Conditions ◽  
Mitochondrial Inner Membrane ◽  
Tube Expansion

Mammalian mitochondrial inner membrane fusion is mediated by optic atrophy 1 (OPA1). Under physiological conditions, OPA1 undergoes proteolytic processing to form a membrane-anchored long isoform (L-OPA1) and a soluble short isoform (S-OPA1). A combination of L-OPA1 and S-OPA1 is essential for efficient membrane fusion; however, the relevant mechanism is not well understood. In this study, we investigate the cryo-electron microscopic structures of S-OPA1–coated liposomes in nucleotide-free and GTPγS-bound states. S-OPA1 exhibits a general dynamin-like structure and can assemble onto membranes in a helical array with a dimer building block. We reveal that hydrophobic residues in its extended membrane-binding domain are critical for its tubulation activity. The binding of GTPγS triggers a conformational change and results in a rearrangement of the helical lattice and tube expansion similar to that of S-Mgm1. These observations indicate that S-OPA1 adopts a dynamin-like power stroke membrane remodeling mechanism during mitochondrial inner membrane fusion.

The Multiple Levels of Mitonuclear Coregulation

2018 ◽  
Vol 52 (1) ◽  
pp. 511-533 ◽  
Author(s):  
R. Stefan Isaac ◽  
Erik McShane ◽  
L. Stirling Churchman
Keyword(s):  
Gene Expression ◽  
Oxidative Phosphorylation ◽  
Protein Degradation ◽  
Current Understanding ◽  
Mitochondrial Genomes ◽  
Expression Systems ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Optimal Function ◽  
Multiple Levels

Together, the nuclear and mitochondrial genomes encode the oxidative phosphorylation (OXPHOS) complexes that reside in the mitochondrial inner membrane and enable aerobic life. Mitochondria maintain their own genome that is expressed and regulated by factors distinct from their nuclear counterparts. For optimal function, the cell must ensure proper stoichiometric production of OXPHOS subunits by coordinating two physically separated and evolutionarily distinct gene expression systems. Here, we review our current understanding of mitonuclear coregulation primarily at the levels of transcription and translation. Additionally, we discuss other levels of coregulation that may exist but remain largely unexplored, including mRNA modification and stability and posttranslational protein degradation.

scholarly journals NME6 is a phosphotransfer-inactive, monomeric NME/NDPK family member and functions in complexes at the interface of mitochondrial inner membrane and matrix

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bastien Proust ◽  
Martina Radić ◽  
Nikolina Škrobot Vidaček ◽  
Cécile Cottet ◽  
Stéphane Attia ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Nucleoside Diphosphate Kinase ◽  
Direct Interaction ◽  
Complex Iii ◽  
Mitochondrial Translation ◽  
Matrix Space ◽  
Inner Membrane ◽  
Network Characteristics ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Ribosome

Abstract Background NME6 is a member of the nucleoside diphosphate kinase (NDPK/NME/Nm23) family which has key roles in nucleotide homeostasis, signal transduction, membrane remodeling and metastasis suppression. The well-studied NME1-NME4 proteins are hexameric and catalyze, via a phospho-histidine intermediate, the transfer of the terminal phosphate from (d)NTPs to (d)NDPs (NDP kinase) or proteins (protein histidine kinase). For the NME6, a gene/protein that emerged early in eukaryotic evolution, only scarce and partially inconsistent data are available. Here we aim to clarify and extend our knowledge on the human NME6. Results We show that NME6 is mostly expressed as a 186 amino acid protein, but that a second albeit much less abundant isoform exists. The recombinant NME6 remains monomeric, and does not assemble into homo-oligomers or hetero-oligomers with NME1-NME4. Consequently, NME6 is unable to catalyze phosphotransfer: it does not generate the phospho-histidine intermediate, and no NDPK activity can be detected. In cells, we could resolve and extend existing contradictory reports by localizing NME6 within mitochondria, largely associated with the mitochondrial inner membrane and matrix space. Overexpressing NME6 reduces ADP-stimulated mitochondrial respiration and complex III abundance, thus linking NME6 to dysfunctional oxidative phosphorylation. However, it did not alter mitochondrial membrane potential, mass, or network characteristics. Our screen for NME6 protein partners revealed its association with NME4 and OPA1, but a direct interaction was observed only with RCC1L, a protein involved in mitochondrial ribosome assembly and mitochondrial translation, and identified as essential for oxidative phosphorylation. Conclusions NME6, RCC1L and mitoribosomes localize together at the inner membrane/matrix space where NME6, in concert with RCC1L, may be involved in regulation of the mitochondrial translation of essential oxidative phosphorylation subunits. Our findings suggest new functions for NME6, independent of the classical phosphotransfer activity associated with NME proteins.

Targeting Dinitrophenol to Mitochondria: Limitations to the Development of a Self-limiting Mitochondrial Protonophore

2006 ◽  
Vol 26 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Frances H. Blaikie ◽  
Stephanie E. Brown ◽  
Linda M. Samuelsson ◽  
Martin D. Brand ◽  
Robin A. J. Smith ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Atp Synthesis ◽  
Proton Leak ◽  
Protonmotive Force ◽  
Inner Membrane ◽  
Atp Production ◽  
Mitochondrial Inner Membrane ◽  
Predominant Component

The protonmotive force (Δp) across the mitochondrial inner membrane drives ATP synthesis. In addition, the energy stored in Δp can be dissipated by proton leak through the inner membrane, contributing to basal metabolic rate and thermogenesis. Increasing mitochondrial proton leak pharmacologically should decrease the efficiency of oxidative phosphorylation and counteract obesity by enabling fatty acids to be oxidised with decreased ATP production. While protonophores such as 2,4-dinitrophenol (DNP) increase mitochondrial proton leak and have been used to treat obesity, a slight increase in DNP concentration above the therapeutically effective dose disrupts mitochondrial function and leads to toxicity. Therefore we set out to develop a less toxic protonophore that would increase proton leak significantly at high Δp but not at low Δp. Our design concept for a potential self-limiting protonophore was to couple the DNP moiety to the lipophilic triphenylphosphonium (TPP) cation and this was achieved by the preparation of 3-(3,5-dinitro-4-hydroxyphenyl)propyltriphenylphosphonium methanesulfonate (MitoDNP). TPP cations accumulate within mitochondria driven by the membrane potential (Δψ), the predominant component of Δp. Our hypothesis was that MitoDNP would accumulate in mitochondria at high Δψ where it would act as a protonophore, but that at lower Δψ the accumulation and uncoupling would be far less. We found that MitoDNP was extensively taken into mitochondria driven by Δψ. However MitoDNP did not uncouple mitochondria as judged by its inability to either increase respiration rate or decrease Δψ. Therefore MitoDNP did not act as a protonophore, probably because the efflux of deprotonated MitoDNP was inhibited.

scholarly journals The Mitochondrial Inner Membrane Protein Mitofilin Controls Cristae Morphology

2005 ◽  
Vol 16 (3) ◽  
pp. 1543-1554 ◽  
Author(s):  
George B. John ◽  
Yonglei Shang ◽  
Li Li ◽  
Christian Renken ◽  
Carmen A. Mannella ◽  
...  
Keyword(s):  
Mitochondrial Function ◽  
Metabolic Flux ◽  
Cellular Proliferation ◽  
Mitochondrial Fission ◽  
Mitochondrial Protein ◽  
Electron Microscopic ◽  
Inner Membrane ◽  
Ultrastructural Studies ◽  
Mitochondrial Inner Membrane ◽  
Inner Membrane Protein

Mitochondria are complex organelles with a highly dynamic distribution and internal organization. Here, we demonstrate that mitofilin, a previously identified mitochondrial protein of unknown function, controls mitochondrial cristae morphology. Mitofilin is enriched in the narrow space between the inner boundary and the outer membranes, where it forms a homotypic interaction and assembles into a large multimeric protein complex. Down-regulation of mitofilin in HeLa cells by using specific small interfering RNA lead to decreased cellular proliferation and increased apoptosis, suggesting abnormal mitochondrial function. Although gross mitochondrial fission and fusion seemed normal, ultrastructural studies revealed disorganized mitochondrial inner membrane. Inner membranes failed to form tubular or vesicular cristae and showed as closely packed stacks of membrane sheets that fused intermittently, resulting in a complex maze of membranous network. Electron microscopic tomography estimated a substantial increase in inner:outer membrane ratio, whereas no cristae junctions were detected. In addition, mitochondria subsequently exhibited increased reactive oxygen species production and membrane potential. Although metabolic flux increased due to mitofilin deficiency, mitochondrial oxidative phosphorylation was not increased accordingly. We propose that mitofilin is a critical organizer of the mitochondrial cristae morphology and thus indispensable for normal mitochondrial function.

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