The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Steffi Gruschke - One of the best experts on this subject based on the ideXlab platform.
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assemBly factors monitor sequential hemylation of <B>CytochromeB> B to regulate mitochondrial translation
Journal of Cell Biology, 2014Co-Authors: Markus Hildenbeutel, Eric L Hegg, Katharina Stephan, Steffi Gruschke, Brigitte MeunierAbstract: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. <B>CytochromeB> 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 <B>CytochromeB> B is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized <B>CytochromeB> B with assemBly factors and structural complex III suBunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of <B>CytochromeB> B through successive assemBly intermediates. Failure to hemylate <B>CytochromeB> B sequesters the CBp3–CBp6 complex in early assemBly intermediates, thereBy causing a reduction in <B>CytochromeB> B synthesis via a feedBack loop that senses hemylation of <B>CytochromeB> B.
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the cBp3 cBp6 complex coordinates <B>CytochromeB> B synthesis with Bc 1 complex assemBly in yeast mitochondria
Journal of Cell Biology, 2012Co-Authors: Steffi Gruschke, Markus Hildenbeutel, Katharina Rompler, Kirsten Kehrein, Inge Kuhl, Nathalie BonnefoyAbstract: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 <B>CytochromeB> B. We recently showed that the CBp3–CBp6 complex has a dual function for Biogenesis of <B>CytochromeB> B: it is Both required for efficient synthesis of <B>CytochromeB> B and for protection of the newly synthesized protein from proteolysis. Here, we report that CBp3–CBp6 also coordinates <B>CytochromeB> B synthesis with Bc1 complex assemBly. We show that newly synthesized <B>CytochromeB> B assemBled through a series of four assemBly intermediates. Blocking assemBly at early and intermediate steps resulted in sequestration of CBp3–CBp6 in a <B>CytochromeB> B–containing complex, thereBy making CBp3–CBp6 unavailaBle for <B>CytochromeB> B synthesis and thus reducing overall <B>CytochromeB> B levels. This feedBack loop regulates protein synthesis at the inner mitochondrial memBrane By directly monitoring the efficiency of Bc1 complex assemBly.
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The timing of heme incorporation into yeast <B>CytochromeB> B
2012Co-Authors: Markus Hildenbeutel, Eric L Hegg, Steffi Gruschke, Brigitte MeunierAbstract:The inner memBrane of mitochondria harBors the complexes of the respiratory chain and the ATP synthase, which perform the key metaBolic process oxidative phosphorylation. These complexes are composed of suBunits from two different genetic origins: the majority of constituents is synthesized on cytosolic riBosomes and imported into mitochondria, But a handful of proteins, which represent core catalytic suBunits, are encoded in the organellar DNA and translated on mitochondrial riBosomes. Using yeast as a model organism, I investigated the mitochondrial riBosomal tunnel exit, the region of the riBosome where the nascent chain emerges and that in cytosolic riBosomes serves as a platform to Bind Biogenesis factors that help the newly synthesized protein to mature. This study provided insights into the structural composition of this important site of mitochondrial riBosomes and revealed the positioning of CBp3 at the tunnel exit region, a chaperone required specifically for the assemBly of the Bc1 complex. In my further work I found that CBp3 structurally and functionally forms a tight complex with CBp6 and that this complex exhiBits fundamental roles in the Biogenesis of <B>CytochromeB> B, the mitochondrially encoded suBunit of the Bc1 complex. Bound to the riBosome, CBp3-CBp6 stimulates translation of the <B>CytochromeB> B mRNA (COB mRNA). CBp3-CBp6 then Binds the fully synthesized <B>CytochromeB> B, thereBy staBilizing and guiding it further through Bc1 complex assemBly. The next steps involve the recruitment of the assemBly factor CBp4 to the CBp3-CBp6/<B>CytochromeB> B complex and presumaBly acquisition of two redox active heme B cofactors. During further assemBly CBp3-CBp6 is released from <B>CytochromeB> B, can again Bind to the riBosome and activate further rounds of COB mRNA translation. The dual role of CBp3-CBp6 in Both translation and assemBly allows the complex to act as a regulatory switch to modulate the level of <B>CytochromeB> B synthesis in response to the Bc1 complex assemBly process.
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cBp3 cBp6 interacts with the yeast mitochondrial riBosomal tunnel exit and promotes <B>CytochromeB> B synthesis and assemBly
Journal of Cell Biology, 2011Co-Authors: Steffi Gruschke, Katharina Rompler, Kirsten Kehrein, Kerstin Grone, Lars Israel, Axel Imhof, Johannes M HerrmannAbstract:Mitochondria contain their own genetic system to express a small numBer of hydrophoBic polypeptides, including <B>CytochromeB> B, an essential suBunit of the Bc1 complex of the respiratory chain. In this paper, we show in yeast that CBp3, a Bc1 complex assemBly factor, and CBp6, a regulator of <B>CytochromeB> B translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial riBosomes and that exhiBits two important functions in the Biogenesis of <B>CytochromeB> B. On the one hand, the interaction of CBp3 and CBp6 with mitochondrial riBosomes is necessary for efficient translation of <B>CytochromeB> B transcript. On the other hand, the CBp3–CBp6 complex interacts directly with newly synthesized <B>CytochromeB> B in an assemBly intermediate that is not riBosome Bound and that contains the assemBly factor CBp4. Our results suggest that synthesis of <B>CytochromeB> B occurs preferentially on those riBosomes that have the CBp3–CBp6 complex Bound to their tunnel exit, an arrangement that may ensure tight coordination of <B>CytochromeB> B synthesis and assemBly.
Rafael Picorel - One of the best experts on this subject based on the ideXlab platform.
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Reconstitution, spectroscopy, and redox properties of the photosynthetic recomBinant <B>CytochromeB> B _559 from higher plants
Photosynthesis Research, 2012Co-Authors: María A. Luján, Jesús I. Martínez, Pablo J. Alonso, Fernando Guerrero, Mercedes Roncel, José M. Ortega, Inmaculada Yruela, Rafael PicorelAbstract:A study of the in vitro reconstitution of sugar Beet <B>CytochromeB> B _559 of the photosystem II is descriBed. Both α and β <B>CytochromeB> suBunits were first cloned and expressed in Escherichia coli . In vitro reconstitution of this <B>CytochromeB> was carried out with partially purified recomBinant suBunits from inclusion Bodies. Reconstitution with commercial heme of Both (αα) and (ββ) homodimers and (αβ) heterodimer was possiBle, the latter Being more efficient. The aBsorption spectra of these reconstituted samples were similar to that of the native heterodimer <B>CytochromeB> B _559 form. As shown By electron paramagnetic resonance and potentiometry, most of the reconstituted <B>CytochromeB> corresponded to a low spin form with a midpoint redox potential +36 mV, similar to that from the native purified <B>CytochromeB> B _559. Furthermore, during the expression of sugar Beet and Synechocystis sp. PCC 6803 <B>CytochromeB> B _559 suBunits, part of the protein suBunits were incorporated into the host Bacterial inner memBrane, But only in the case of the β suBunit from the cyanoBacterium the formation of a <B>CytochromeB> B _559-like structure with the Bacterial endogenous heme was oBserved. The reason for that surprising result is unknown. This in vivo formed (ββ) homodimer <B>CytochromeB> B _559-like structure showed similar aBsorption and electron paramagnetic resonance spectral properties as the native purified <B>CytochromeB> B _559. A higher midpoint redox potential (+126 mV) was detected in the in vivo formed protein compared to the in vitro reconstituted form, most likely due to a more hydrophoBic environment imposed By the lipid memBrane surrounding the heme.
Kirsten Kehrein - One of the best experts on this subject based on the ideXlab platform.
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the cBp3 cBp6 complex coordinates <B>CytochromeB> B synthesis with Bc 1 complex assemBly in yeast mitochondria
Journal of Cell Biology, 2012Co-Authors: Steffi Gruschke, Markus Hildenbeutel, Katharina Rompler, Kirsten Kehrein, Inge Kuhl, Nathalie BonnefoyAbstract: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 <B>CytochromeB> B. We recently showed that the CBp3–CBp6 complex has a dual function for Biogenesis of <B>CytochromeB> B: it is Both required for efficient synthesis of <B>CytochromeB> B and for protection of the newly synthesized protein from proteolysis. Here, we report that CBp3–CBp6 also coordinates <B>CytochromeB> B synthesis with Bc1 complex assemBly. We show that newly synthesized <B>CytochromeB> B assemBled through a series of four assemBly intermediates. Blocking assemBly at early and intermediate steps resulted in sequestration of CBp3–CBp6 in a <B>CytochromeB> B–containing complex, thereBy making CBp3–CBp6 unavailaBle for <B>CytochromeB> B synthesis and thus reducing overall <B>CytochromeB> B levels. This feedBack loop regulates protein synthesis at the inner mitochondrial memBrane By directly monitoring the efficiency of Bc1 complex assemBly.
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cBp3 cBp6 interacts with the yeast mitochondrial riBosomal tunnel exit and promotes <B>CytochromeB> B synthesis and assemBly
Journal of Cell Biology, 2011Co-Authors: Steffi Gruschke, Katharina Rompler, Kirsten Kehrein, Kerstin Grone, Lars Israel, Axel Imhof, Johannes M HerrmannAbstract:Mitochondria contain their own genetic system to express a small numBer of hydrophoBic polypeptides, including <B>CytochromeB> B, an essential suBunit of the Bc1 complex of the respiratory chain. In this paper, we show in yeast that CBp3, a Bc1 complex assemBly factor, and CBp6, a regulator of <B>CytochromeB> B translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial riBosomes and that exhiBits two important functions in the Biogenesis of <B>CytochromeB> B. On the one hand, the interaction of CBp3 and CBp6 with mitochondrial riBosomes is necessary for efficient translation of <B>CytochromeB> B transcript. On the other hand, the CBp3–CBp6 complex interacts directly with newly synthesized <B>CytochromeB> B in an assemBly intermediate that is not riBosome Bound and that contains the assemBly factor CBp4. Our results suggest that synthesis of <B>CytochromeB> B occurs preferentially on those riBosomes that have the CBp3–CBp6 complex Bound to their tunnel exit, an arrangement that may ensure tight coordination of <B>CytochromeB> B synthesis and assemBly.
Brigitte Meunier - One of the best experts on this subject based on the ideXlab platform.
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assemBly factors monitor sequential hemylation of <B>CytochromeB> B to regulate mitochondrial translation
Journal of Cell Biology, 2014Co-Authors: Markus Hildenbeutel, Eric L Hegg, Katharina Stephan, Steffi Gruschke, Brigitte MeunierAbstract: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. <B>CytochromeB> 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 <B>CytochromeB> B is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized <B>CytochromeB> B with assemBly factors and structural complex III suBunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of <B>CytochromeB> B through successive assemBly intermediates. Failure to hemylate <B>CytochromeB> B sequesters the CBp3–CBp6 complex in early assemBly intermediates, thereBy causing a reduction in <B>CytochromeB> B synthesis via a feedBack loop that senses hemylation of <B>CytochromeB> B.
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The timing of heme incorporation into yeast <B>CytochromeB> B
2012Co-Authors: Markus Hildenbeutel, Eric L Hegg, Steffi Gruschke, Brigitte MeunierAbstract:The inner memBrane of mitochondria harBors the complexes of the respiratory chain and the ATP synthase, which perform the key metaBolic process oxidative phosphorylation. These complexes are composed of suBunits from two different genetic origins: the majority of constituents is synthesized on cytosolic riBosomes and imported into mitochondria, But a handful of proteins, which represent core catalytic suBunits, are encoded in the organellar DNA and translated on mitochondrial riBosomes. Using yeast as a model organism, I investigated the mitochondrial riBosomal tunnel exit, the region of the riBosome where the nascent chain emerges and that in cytosolic riBosomes serves as a platform to Bind Biogenesis factors that help the newly synthesized protein to mature. This study provided insights into the structural composition of this important site of mitochondrial riBosomes and revealed the positioning of CBp3 at the tunnel exit region, a chaperone required specifically for the assemBly of the Bc1 complex. In my further work I found that CBp3 structurally and functionally forms a tight complex with CBp6 and that this complex exhiBits fundamental roles in the Biogenesis of <B>CytochromeB> B, the mitochondrially encoded suBunit of the Bc1 complex. Bound to the riBosome, CBp3-CBp6 stimulates translation of the <B>CytochromeB> B mRNA (COB mRNA). CBp3-CBp6 then Binds the fully synthesized <B>CytochromeB> B, thereBy staBilizing and guiding it further through Bc1 complex assemBly. The next steps involve the recruitment of the assemBly factor CBp4 to the CBp3-CBp6/<B>CytochromeB> B complex and presumaBly acquisition of two redox active heme B cofactors. During further assemBly CBp3-CBp6 is released from <B>CytochromeB> B, can again Bind to the riBosome and activate further rounds of COB mRNA translation. The dual role of CBp3-CBp6 in Both translation and assemBly allows the complex to act as a regulatory switch to modulate the level of <B>CytochromeB> B synthesis in response to the Bc1 complex assemBly process.
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Effects of mutations in mitochondrial <B>CytochromeB> B in yeast and man
FEBS Journal, 2001Co-Authors: Nicholas Fisher, Brigitte MeunierAbstract:The mitochondrial <B>CytochromeB> Bc1 complex is a key protonmotive component of eukaryotic respiratory chains. The mitochondrially encoded <B>CytochromeB> B forms, with <B>CytochromeB> c1 and the iron–sulfur protein, the catalytic core of this multimeric enzyme. Mutations of <B>CytochromeB> B have Been reported in association with human diseases. In the highly homologous yeast <B>CytochromeB> B, several mutations that impair the respiratory function, and reversions that correct the defect, have Been descriBed. In this paper, we re-examine the mutations in the light of the atomic structure of the complex, and discuss the possiBle effect, at enzyme level, of the human <B>CytochromeB> B mutations and the correcting effect of the reversions.
Markus Hildenbeutel - One of the best experts on this subject based on the ideXlab platform.
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assemBly factors monitor sequential hemylation of <B>CytochromeB> B to regulate mitochondrial translation
Journal of Cell Biology, 2014Co-Authors: Markus Hildenbeutel, Eric L Hegg, Katharina Stephan, Steffi Gruschke, Brigitte MeunierAbstract: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. <B>CytochromeB> 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 <B>CytochromeB> B is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized <B>CytochromeB> B with assemBly factors and structural complex III suBunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of <B>CytochromeB> B through successive assemBly intermediates. Failure to hemylate <B>CytochromeB> B sequesters the CBp3–CBp6 complex in early assemBly intermediates, thereBy causing a reduction in <B>CytochromeB> B synthesis via a feedBack loop that senses hemylation of <B>CytochromeB> B.
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the cBp3 cBp6 complex coordinates <B>CytochromeB> B synthesis with Bc 1 complex assemBly in yeast mitochondria
Journal of Cell Biology, 2012Co-Authors: Steffi Gruschke, Markus Hildenbeutel, Katharina Rompler, Kirsten Kehrein, Inge Kuhl, Nathalie BonnefoyAbstract: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 <B>CytochromeB> B. We recently showed that the CBp3–CBp6 complex has a dual function for Biogenesis of <B>CytochromeB> B: it is Both required for efficient synthesis of <B>CytochromeB> B and for protection of the newly synthesized protein from proteolysis. Here, we report that CBp3–CBp6 also coordinates <B>CytochromeB> B synthesis with Bc1 complex assemBly. We show that newly synthesized <B>CytochromeB> B assemBled through a series of four assemBly intermediates. Blocking assemBly at early and intermediate steps resulted in sequestration of CBp3–CBp6 in a <B>CytochromeB> B–containing complex, thereBy making CBp3–CBp6 unavailaBle for <B>CytochromeB> B synthesis and thus reducing overall <B>CytochromeB> B levels. This feedBack loop regulates protein synthesis at the inner mitochondrial memBrane By directly monitoring the efficiency of Bc1 complex assemBly.
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The timing of heme incorporation into yeast <B>CytochromeB> B
2012Co-Authors: Markus Hildenbeutel, Eric L Hegg, Steffi Gruschke, Brigitte MeunierAbstract:The inner memBrane of mitochondria harBors the complexes of the respiratory chain and the ATP synthase, which perform the key metaBolic process oxidative phosphorylation. These complexes are composed of suBunits from two different genetic origins: the majority of constituents is synthesized on cytosolic riBosomes and imported into mitochondria, But a handful of proteins, which represent core catalytic suBunits, are encoded in the organellar DNA and translated on mitochondrial riBosomes. Using yeast as a model organism, I investigated the mitochondrial riBosomal tunnel exit, the region of the riBosome where the nascent chain emerges and that in cytosolic riBosomes serves as a platform to Bind Biogenesis factors that help the newly synthesized protein to mature. This study provided insights into the structural composition of this important site of mitochondrial riBosomes and revealed the positioning of CBp3 at the tunnel exit region, a chaperone required specifically for the assemBly of the Bc1 complex. In my further work I found that CBp3 structurally and functionally forms a tight complex with CBp6 and that this complex exhiBits fundamental roles in the Biogenesis of <B>CytochromeB> B, the mitochondrially encoded suBunit of the Bc1 complex. Bound to the riBosome, CBp3-CBp6 stimulates translation of the <B>CytochromeB> B mRNA (COB mRNA). CBp3-CBp6 then Binds the fully synthesized <B>CytochromeB> B, thereBy staBilizing and guiding it further through Bc1 complex assemBly. The next steps involve the recruitment of the assemBly factor CBp4 to the CBp3-CBp6/<B>CytochromeB> B complex and presumaBly acquisition of two redox active heme B cofactors. During further assemBly CBp3-CBp6 is released from <B>CytochromeB> B, can again Bind to the riBosome and activate further rounds of COB mRNA translation. The dual role of CBp3-CBp6 in Both translation and assemBly allows the complex to act as a regulatory switch to modulate the level of <B>CytochromeB> B synthesis in response to the Bc1 complex assemBly process.
