scholarly journals The Cbp3–Cbp6 complex coordinates cytochrome b synthesis with bc1 complex assembly in yeast mitochondria

2012 ◽  
Vol 199 (1) ◽  
pp. 137-150 ◽  
Author(s):  
Steffi Gruschke ◽  
Katharina Römpler ◽  
Markus Hildenbeutel ◽  
Kirsten Kehrein ◽  
Inge Kühl ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Mitochondrial Membrane ◽  
Feedback Loop ◽  
Dual Function ◽  
Bc1 Complex ◽  
Efficient Synthesis ◽  
Inner Mitochondrial Membrane ◽  
Respiratory Chain Complexes ◽  
Complex Assembly ◽  
Chain Complexes

Respiratory chain complexes in mitochondria are assembled from subunits derived from two genetic systems. For example, the bc1 complex consists of nine nuclear encoded subunits and the mitochondrially encoded subunit cytochrome b. We recently showed that the Cbp3–Cbp6 complex has a dual function for biogenesis of cytochrome b: it is both required for efficient synthesis of cytochrome b and for protection of the newly synthesized protein from proteolysis. Here, we report that Cbp3–Cbp6 also coordinates cytochrome b synthesis with bc1 complex assembly. We show that newly synthesized cytochrome b assembled through a series of four assembly intermediates. Blocking assembly at early and intermediate steps resulted in sequestration of Cbp3–Cbp6 in a cytochrome b–containing complex, thereby making Cbp3–Cbp6 unavailable for cytochrome b synthesis and thus reducing overall cytochrome b levels. This feedback loop regulates protein synthesis at the inner mitochondrial membrane by directly monitoring the efficiency of bc1 complex assembly.

scholarly journals Assembly factors monitor sequential hemylation of cytochrome b to regulate mitochondrial translation

2014 ◽  
Vol 205 (4) ◽  
pp. 511-524 ◽  
Author(s):  
Markus Hildenbeutel ◽  
Eric L. Hegg ◽  
Katharina Stephan ◽  
Steffi Gruschke ◽  
Brigitte Meunier ◽  
...  
Keyword(s):  
Electron Transport ◽  
Cytochrome B ◽  
Mitochondrial Respiratory Chain ◽  
Complex Iii ◽  
Mitochondrial Translation ◽  
Respiratory Chain Complexes ◽  
Mitochondrial Inner Membrane ◽  
Sequence Of Events ◽  
Chain Complexes ◽  
Assembly Factors

Mitochondrial respiratory chain complexes convert chemical energy into a membrane potential by connecting electron transport with charge separation. Electron transport relies on redox cofactors that occupy strategic positions in the complexes. How these redox cofactors are assembled into the complexes is not known. Cytochrome b, a central catalytic subunit of complex III, contains two heme bs. Here, we unravel the sequence of events in the mitochondrial inner membrane by which cytochrome b is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized cytochrome b with assembly factors and structural complex III subunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of cytochrome b through successive assembly intermediates. Failure to hemylate cytochrome b sequesters the Cbp3–Cbp6 complex in early assembly intermediates, thereby causing a reduction in cytochrome b synthesis via a feedback loop that senses hemylation of cytochrome b.

scholarly journals Respiratory chain supercomplexes associate with the cysteine desulfurase complex of the iron–sulfur cluster assembly machinery

2018 ◽  
Vol 29 (7) ◽  
pp. 776-785 ◽  
Author(s):  
Lena Böttinger ◽  
Christoph U. Mårtensson ◽  
Jiyao Song ◽  
Nicole Zufall ◽  
Nils Wiedemann ◽  
...  
Keyword(s):  
Respiratory Chain ◽  
Complex Iii ◽  
Bc1 Complex ◽  
Cytochrome Bc1 Complex ◽  
Respiratory Chain Complexes ◽  
Cysteine Desulfurase ◽  
Complex Iv ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur ◽  
Chain Complexes

Mitochondria are the powerhouses of eukaryotic cells. The activity of the respiratory chain complexes generates a proton gradient across the inner membrane, which is used by the F1FO-ATP synthase to produce ATP for cellular metabolism. In baker’s yeast, Saccharomyces cerevisiae, the cytochrome bc1 complex (complex III) and cytochrome c oxidase (complex IV) associate in respiratory chain supercomplexes. Iron–sulfur clusters (ISC) form reactive centers of respiratory chain complexes. The assembly of ISC occurs in the mitochondrial matrix and is essential for cell viability. The cysteine desulfurase Nfs1 provides sulfur for ISC assembly and forms with partner proteins the ISC-biogenesis desulfurase complex (ISD complex). Here, we report an unexpected interaction of the active ISD complex with the cytochrome bc1 complex and cytochrome c oxidase. The individual deletion of complex III or complex IV blocks the association of the ISD complex with respiratory chain components. We conclude that the ISD complex binds selectively to respiratory chain supercomplexes. We propose that this molecular link contributes to coordination of iron–sulfur cluster formation with respiratory activity.

scholarly journals The cytochrome b p.278Y>C mutation causative of a multisystem disorder enhances superoxide production and alters supramolecular interactions of respiratory chain complexes

2013 ◽  
Vol 22 (11) ◽  
pp. 2141-2151 ◽  
Author(s):  
Anna Ghelli ◽  
Concetta V. Tropeano ◽  
Maria Antonietta Calvaruso ◽  
Alessandra Marchesini ◽  
Luisa Iommarini ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Respiratory Chain ◽  
Superoxide Production ◽  
Supramolecular Interactions ◽  
Multisystem Disorder ◽  
Respiratory Chain Complexes ◽  
Chain Complexes

scholarly journals ANT1 Activation and Inhibition Patterns Support the Fatty Acid Cycling Mechanism for Proton Transport

2021 ◽  
Vol 22 (5) ◽  
pp. 2490
Author(s):  
Jürgen Kreiter ◽  
Anne Rupprecht ◽  
Sanja Škulj ◽  
Zlatko Brkljača ◽  
Kristina Žuna ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Lipid Bilayers ◽  
Proton Transport ◽  
Mitochondrial Membrane ◽  
Adenine Nucleotide ◽  
Molecular Transport ◽  
Correlation Spectroscopy ◽  
Dual Function ◽  
Inner Mitochondrial Membrane ◽  
Purine Nucleotides

Adenine nucleotide translocase (ANT) is a well-known mitochondrial exchanger of ATP against ADP. In contrast, few studies have shown that ANT also mediates proton transport across the inner mitochondrial membrane. The results of these studies are controversial and lead to different hypotheses about molecular transport mechanisms. We hypothesized that the H+-transport mediated by ANT and uncoupling proteins (UCP) has a similar regulation pattern and can be explained by the fatty acid cycling concept. The reconstitution of purified recombinant ANT1 in the planar lipid bilayers allowed us to measure the membrane current after the direct application of transmembrane potential ΔΨ, which would correspond to the mitochondrial states III and IV. Experimental results reveal that ANT1 does not contribute to a basal proton leak. Instead, it mediates H+ transport only in the presence of long-chain fatty acids (FA), as already known for UCPs. It depends on FA chain length and saturation, implying that FA’s transport is confined to the lipid-protein interface. Purine nucleotides with the preference for ATP and ADP inhibited H+ transport. Specific inhibitors of ATP/ADP transport, carboxyatractyloside or bongkrekic acid, also decreased proton transport. The H+ turnover number was calculated based on ANT1 concentration determined by fluorescence correlation spectroscopy and is equal to 14.6 ± 2.5 s−1. Molecular dynamic simulations revealed a large positively charged area at the protein/lipid interface that might facilitate FA anion’s transport across the membrane. ANT’s dual function—ADP/ATP and H+ transport in the presence of FA—may be important for the regulation of mitochondrial membrane potential and thus for potential-dependent processes in mitochondria. Moreover, the expansion of proton-transport modulating drug targets to ANT1 may improve the therapy of obesity, cancer, steatosis, cardiovascular and neurodegenerative diseases.

scholarly journals Taz1, an Outer Mitochondrial Membrane Protein, Affects Stability and Assembly of Inner Membrane Protein Complexes: Implications for Barth Syndrome

2005 ◽  
Vol 16 (11) ◽  
pp. 5202-5214 ◽  
Author(s):  
Katrin Brandner ◽  
David U. Mick ◽  
Ann E. Frazier ◽  
Rebecca D. Taylor ◽  
Chris Meisinger ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Respiratory Chain ◽  
Mitochondrial Membrane ◽  
Barth Syndrome ◽  
Outer Mitochondrial Membrane ◽  
Respiratory Chain Complexes ◽  
Complex Iv ◽  
Inner Membrane ◽  
Chain Complexes ◽  
Mitochondrial Membrane Protein

The Saccharomyces cerevisiae Taz1 protein is the orthologue of human Tafazzin, a protein that when inactive causes Barth Syndrome (BTHS), a severe inherited X-linked disease. Taz1 is a mitochondrial acyltransferase involved in the remodeling of cardiolipin. We show that Taz1 is an outer mitochondrial membrane protein exposed to the intermembrane space (IMS). Transport of Taz1 into mitochondria depends on the receptor Tom5 of the translocase of the outer membrane (TOM complex) and the small Tim proteins of the IMS, but is independent of the sorting and assembly complex (SAM). TAZ1 deletion in yeast leads to growth defects on nonfermentable carbon sources, indicative of a defect in respiration. Because cardiolipin has been proposed to stabilize supercomplexes of the respiratory chain complexes III and IV, we assess supercomplexes in taz1Δ mitochondria and show that these are destabilized in taz1Δ mitochondria. This leads to a selective release of a complex IV monomer from the III2IV2 supercomplex. In addition, assembly analyses of newly imported subunits into complex IV show that incorporation of the complex IV monomer into supercomplexes is affected in taz1Δ mitochondria. We conclude that inactivation of Taz1 affects both assembly and stability of respiratory chain complexes in the inner membrane of mitochondria.

scholarly journals Mitochondrial DNA Depletion and Respiratory Chain Activity in Primary Human Subcutaneous Adipocytes Treated with Nucleoside Analogue Reverse Transcriptase Inhibitors

2009 ◽  
Vol 54 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Metodi V. Stankov ◽  
Thomas Lücke ◽  
Anibh M. Das ◽  
Reinhold E. Schmidt ◽  
Georg M. N. Behrens
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Respiratory Chain ◽  
Mitochondrial Membrane ◽  
Reverse Transcriptase Inhibitors ◽  
Respiratory Chain Complexes ◽  
Mitochondrial Mass ◽  
Mtdna Depletion ◽  
Chain Complexes ◽  
Respiratory Chain Activity

ABSTRACT Mitochondrial dysfunction as a consequence of mitochondrial DNA (mtDNA) depletion due to therapy with nucleoside analogue reverse transcriptase inhibitors (NRTI) has been proposed as a pathogenic mechanism leading to lipoatrophy in HIV-infected patients. The aim of our study was to investigate the impact of NRTI treatment on mtDNA abundance and the activities of respiratory chain complexes in primary human subcutaneous preadipocytes (phsPA). We studied adipocyte phenotypes, viability, and differentiation (CCAAT/enhancer-binding protein α [C/EBPα] and peroxisome proliferator-activated receptor γ [PPARγ] expression) and adiponectin production, mtDNA content, mitochondrial membrane potential, mitochondrial mass, and respiratory chain enzyme and citrate synthase activities in both proliferating and differentiating phsPA. Cells were exposed to zidovudine (6 μM), stavudine (d4T; 3 μM), and zalcitabine (ddC; 0.1 μM) for 8 weeks. NRTI-induced mtDNA depletion occurred in proliferating and differentiating phsPA after exposure to therapeutic drug concentrations of d4T and ddC. At these concentrations, ddC and d4T led to an almost 50% decrease in the number of mtDNA copies per cell without major impact on adipocyte differentiation. Despite mtDNA depletion by NRTI, the activities of the respiratory chain complexes, the mitochondrial membrane potential, and the mitochondrial mass were found to be unaffected. Severe NRTI-mediated mtDNA depletion in phsPA is not inevitably associated with impaired respiratory chain activity or altered mitochondrial membrane potential.

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