scholarly journals Mutations in the Membrane Anchor of Yeast Cytochrome c1 Compensate for the Absence of Oxa1p and Generate Carbonate-Extractable Forms of Cytochrome c1

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 601-611
Author(s):  
Patrice Hamel ◽  
Claire Lemaire ◽  
Nathalie Bonnefoy ◽  
Paule Brivet-Chevillotte ◽  
Geneviève Dujardin
Keyword(s):  
Electron Transfer ◽  
Complex Iii ◽  
Membrane Anchor ◽  
Suppressor Activity ◽  
Complex Iv ◽  
Transfer Activity ◽  
Suppressor Function ◽  
Mitochondrial Inner Membrane ◽  
Cytochrome C1 ◽  
Inner Membrane Protein

Abstract Oxa1p is a mitochondrial inner membrane protein that is mainly required for the insertion/assembly of complex IV and ATP synthase and is functionally conserved in yeasts, humans, and plants. We have isolated several independent suppressors that compensate for the absence of Oxa1p. Molecular cloning and sequencing reveal that the suppressor mutations (CYT1-1 to -6) correspond to amino acid substitutions that are all located in the membrane anchor of cytochrome c1 and decrease the hydrophobicity of this anchor. Cytochrome c1 is a catalytic subunit of complex III, but the CYT1-1 mutation does not seem to affect the electron transfer activity. The double-mutant cyt1-1,164, which has a drastically reduced electron transfer activity, still retains the suppressor activity. Altogether, these results suggest that the suppressor function of cytochrome c1 is independent of its electron transfer activity. In addition to the membranebound cytochrome c1, carbonate-extractable forms accumulate in all the suppressor strains. We propose that these carbonate-extractable forms of cytochrome c1 are responsible for the suppressor function by preventing the degradation of the respiratory complex subunits that occur in the absence of Oxa1p.

scholarly journals Structural and Functional Association of Trypanosoma brucei MIX Protein with Cytochrome c Oxidase Complex

2008 ◽  
Vol 7 (11) ◽  
pp. 1994-2003 ◽  
Author(s):  
Alena Zíková ◽  
Aswini K. Panigrahi ◽  
Alessandro D. Uboldi ◽  
Rachel A. Dalley ◽  
Emanuela Handman ◽  
...  
Keyword(s):  
Cell Division ◽  
Trypanosoma Brucei ◽  
Leishmania Major ◽  
Affinity Purification ◽  
Major Effect ◽  
Multiprotein Complex ◽  
Complex Iv ◽  
Mitochondrial Inner Membrane ◽  
Single Allele ◽  
Inner Membrane Protein

ABSTRACT A mitochondrial inner membrane protein, designated MIX, seems to be essential for cell viability. The deletion of both alleles was not possible, and the deletion of a single allele led to a loss of virulence and aberrant mitochondrial segregation and cell division in Leishmania major. However, the mechanism by which MIX exerts its effect has not been determined. We show here that MIX is also expressed in the mitochondrion of Trypanosoma brucei, and using RNA interference, we found that its loss leads to a phenotype that is similar to that described for Leishmania. The loss of MIX also had a major effect on cytochrome c oxidase activity, on the mitochondrial membrane potential, and on the production of mitochondrial ATP by oxidative phosphorylation. Using a tandem affinity purification tag, we found that MIX is associated with a multiprotein complex that contains subunits of the mitochondrial cytochrome c oxidase complex (respiratory complex IV), the composition of which was characterized in detail. The specific function of MIX is unknown, but it appears to be important for the function of complex IV and for mitochondrial segregation and cell division in T. brucei.

The crystalline structure in the membranous preparations of mitochondrial complex III

1978 ◽  
Vol 36 (2) ◽  
pp. 292-293
Author(s):  
Junpei Asai
Keyword(s):  
Electron Transfer ◽  
Complex Iii ◽  
Molecular Architecture ◽  
Membrane Formation ◽  
Electron Transfer Chain ◽  
Ultrastructural Studies ◽  
Mitochondrial Inner Membrane ◽  
Beef Heart Mitochondria ◽  
The Individual ◽  
Transfer Chain

In 1962 Hatefi and his collegues showed biochemically the isolation of four complexes of the electron transfer chain from the mitochondria and the reconstitution of a complete electron transfer chain through re-association of the individual complexes. Tzagoloff et al demonstrated ultrastructurally the membrane formation by either single complex or a mixture of complexs. However, there have been a few direct ultrastructural studies in the molecular architecture of mitochondrial inner membrane. To understand the organization of Complex III (QH2-cytochrome c reductase) in the membrane, the membranes made from this complex under various conditions were examined ultrastructurally in the present study.Complex III was purified from beef heart mitochondria by the method of Heatefi et al as modified by Rieske et al. For the preparations of membrane formation, some samples of the purified complex suspended in the solution contained 0.66 M sucrose were diluted with 100 volumes of the mixture of 0.25 M in sucrose and 0.01 M in Tris-HCl (sucrose-Tris), pH 8.0 and were incubated for 30 min. at 0-4°C.

scholarly journals Divergences in the control of mitochondrial respiration are associated with lifespan variation in marine bivalves

2020 ◽  
Author(s):  
Enrique Rodríguez ◽  
Mohammed Hakkou ◽  
Tory M Hagen ◽  
Hélène Lemieux ◽  
Pierre U Blier
Keyword(s):  
Oxidative Stress ◽  
Electron Transfer ◽  
Complex Iii ◽  
Control Analysis ◽  
Transfer System ◽  
Complex Iv ◽  
Flux Control ◽  
Electron Transfer System ◽  
Marine Bivalves ◽  
Strong Control

Abstract The role played by mitochondrial function in the aging process has been a subject of intense debate in the past few decades, as part of the efforts to understand the mechanistic basis of longevity. The mitochondrial oxidative stress theory of aging (MOSTA) suggests that a progressive decay of this organelle’s function leads to an exacerbation of oxidative stress, with deleterious impact on mitochondrial structure and DNA, ultimately promoting aging. Among the traits suspected to be associated with longevity is the variation in regulation of oxidative phosphorylation, potentially impacting the management of oxidative stress. Longitudinal studies using the framework of metabolic control analysis have shown age-related differences in flux control of respiration, but this approach has seldom been taken on a comparative scale. Using four species of marine bivalves exhibiting a large range of maximum lifespans (from 28y to 507y), we report lifespan-related differences in flux control at different steps of the electron transfer system. Increased longevity was characterized by a lower control by NADH- (complex I-linked) and Succinate- (complex II- linked) pathways, while respiration was strongly controlled by complex IV when compared to shorter-lived species. Complex III exterted a strong control over respiration in all species. Furthermore, high longevity was associated with higher citrate synthase activity, and lower ATP synthase activity. Relieving the control exerted by the electron entry pathways could be advantageous for reaching a higher longevity, leading to an increased control by complex IV, the final electron acceptor in the electron transfer system.

scholarly journals Super-resolution microscopy reveals arrangement of inner membrane protein complexes in mammalian mitochondria

2021 ◽  
Author(s):  
Catherine S. Palmer ◽  
Jieqiong Lou ◽  
Betty Kouskousis ◽  
Elvis Pandzic ◽  
Alexander J. Anderson ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Protein Complexes ◽  
Super Resolution ◽  
Bimodal Distribution ◽  
Complex Iv ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Cellular Context ◽  
Inner Membrane Protein ◽  
Super Resolution Microscopy

The mitochondrial inner membrane is a protein rich environment containing large multimeric complexes including complexes of the mitochondrial electron transport chain, mitochondrial translocases and quality control machineries. Although the inner membrane is highly proteinaceous, with 40–60% of all mitochondrial proteins localised to this compartment, little is known about the spatial distribution and organisation of complexes in this environment. We set out to survey the arrangement of inner membrane complexes using stochastic optical reconstruction microscopy (STORM). We show subunits of the TIM23 Complex, Tim23 and Tim44, and the Complex IV subunit COXIV form organised clusters and show distinct properties to the outer membrane protein Tom20. Density based cluster analysis indicated a bimodal distribution of Tim44 that is distinct from Tim23, suggesting distinct TIM23 subcomplexes. COXIV is arranged in larger clusters, that are disrupted upon disruption of Complex IV assembly. Thus, STORM super-resolution microscopy is a powerful approach to examine the nanoscale distribution of mitochondrial inner membrane complexes, providing a “visual” approach to obtaining pivotal information on how mitochondrial complexes exist in a cellular context.

scholarly journals An electron transfer path connects subunits of a mycobacterial respiratory supercomplex

Science ◽  
2018 ◽  
Vol 362 (6418) ◽  
pp. eaat8923 ◽  
Author(s):  
Hongri Gong ◽  
Jun Li ◽  
Ao Xu ◽  
Yanting Tang ◽  
Wenxin Ji ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Superoxide Dismutase ◽  
Oxygen Reduction ◽  
Mycobacterium Smegmatis ◽  
Drug Target ◽  
Complex Iii ◽  
Complex Iv ◽  
Transfer Path ◽  
Cryo Electron Microscopy

We report a 3.5-angstrom-resolution cryo–electron microscopy structure of a respiratory supercomplex isolated fromMycobacterium smegmatis.It comprises a complex III dimer flanked on either side by individual complex IV subunits. Complex III and IV associate so that electrons can be transferred from quinol in complex III to the oxygen reduction center in complex IV by way of a bridging cytochrome subunit. We observed a superoxide dismutase-like subunit at the periplasmic face, which may be responsible for detoxification of superoxide formed by complex III. The structure reveals features of an established drug target and provides a foundation for the development of treatments for human tuberculosis.

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