The C‐terminus of the 14‐kDa subunit of ubiquinol‐cytochrome‐<i>c</i> oxidoreductase of the yeast <i>Saccharomyces cerevisiae</i> is involved in the assembly of a functional enzyme

Hemrika, Wieger; Jong, Marianne de; Berden, J.A.; Grivell, Leslie A.

doi:10.1111/j.1432-1033.1994.tb18657.x

Cited by 20 publications

(12 citation statements)

References 39 publications

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“…Another interesting feature of this region is that five positions in the alignment contain more than 50% glutamate residues. A previous study on this C-terminus in S. cerevisiae showed the importance of this part of the protein for correct assembly of the bcj complex, but not for electron transport [25]. The study also implied that the overall features of this region (hydrophilicity and charges) rather than specific residues are important, a feature which is confirmed by the sequence alignment in Fig.…”

Section: Discussionsupporting

confidence: 69%

Identification of additional homologues of subunits VII and VIII of the ubiquinol‐cytochrome c oxidoreductase enables definition of consensus sequences

1995

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The Candida utilis QCR7 gene encoding subunit VII of the ubiquinol-cytochrome c oxidoreductase was isolated by functional complementation of the Saccharomyces cerevisiae subunit VII-null mutant. Several other subunit VII homologues as well as homologues for subunit VIII were identified by screening the GenBank database. Some of these homologues for subunit VII could only be identified as such using a consensus sequence that was derived from the multiple sequence alignment. Definition of the consensus should facilitate further analysis of structure/ function relationships in this protein.

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Section: Discussionsupporting

confidence: 69%

Identification of additional homologues of subunits VII and VIII of the ubiquinol‐cytochrome c oxidoreductase enables definition of consensus sequences

1995

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“…UQCRB is known to play a pivotal role in the assembly and maintenance of Complex III, which is conserved in the respiratory chain of all aerobic organisms as well as in the electron transfer systems of chloroplasts and photosynthetic bacteria (34,35). Hereditary defects in the UQCRB gene cause several mitochondrial diseases such as hypoglycemia, lactic acidosis, myopathy, and cardiomyopathy (36,37), which are partially associated with deregulation of angiogenesis (38,39).…”

Section: Terpestacin Modulates the O 2 -Sensing Function Of Complex Imentioning

confidence: 99%

Terpestacin Inhibits Tumor Angiogenesis by Targeting UQCRB of Mitochondrial Complex III and Suppressing Hypoxia-induced Reactive Oxygen Species Production and Cellular Oxygen Sensing

Jung

Shim

Lee

et al. 2010

Journal of Biological Chemistry

109

102

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Cellular oxygen sensing is required for hypoxia-inducible factor-1␣ stabilization, which is important for tumor cell survival, proliferation, and angiogenesis. Here we find that terpestacin, a small molecule previously identified in a screen of microbial extracts, binds to the 13.4-kDa subunit (UQCRB) of mitochondrial Complex III, resulting in inhibition of hypoxia-induced reactive oxygen species generation. Consequently, such inhibition blocks hypoxia-inducible factor activation and tumor angiogenesis in vivo, without inhibiting mitochondrial respiration. Overexpression of UQCRB or its suppression using RNA interference demonstrates that it plays a crucial role in the oxygen sensing mechanism that regulates responses to hypoxia. These findings provide a novel molecular basis of terpestacin targeting UQCRB of Complex III in selective suppression of tumor progression.Progression of many solid tumors requires angiogenesis (1). Mitochondrial function has been linked to angiogenesis, because mitochondria are the primary sites of oxygen consumption, and angiogenesis is an oxygen concentration-sensitive process (2). Reports suggest that reactive oxygen species (ROS) 3 generation at mitochondrial Complex III is necessary and sufficient to trigger HIF-1␣ stabilization during hypoxia, and cells lacking mitochondrial DNA and electron transport activity ( cells) fail to exhibit increased ROS or up-regulation of HIF-1␣ target genes during hypoxia (3-5). Inhibitors of Complex III such as myxothiazol and stigmatellin also block mitochondrial ROS generation and inhibit the stabilization and transcriptional activity of HIF-1␣ during hypoxia. These findings suggest that the generation of ROS from mitochondrial Complex III is a critical event in the signaling of cellular hypoxia (6, 7). However, details regarding which of the components of Complex III contribute to this signaling remain to be described.Biological screening tools are useful for identifying naturally occurring small molecules capable of inducing a specific phenotype change (8, 9). We performed a large scale screen of microbial extracts in an attempt to identify small molecules that could inhibit the angiogenic response to pro-angiogenic stimuli, such as hypoxia, in endothelial cells. We identified terpestacin as a small molecule with unique bicyclo sesterterpene structure capable of inhibiting the angiogenic response at concentrations below the toxic threshold (10). Terpestacin strongly inhibits the functional response to hypoxia of human umbilical vein endothelial cells in vitro and angiogenesis within the embryonic chick chorioallantoic membrane in vivo. In addition to this anti-angiogenic activity, terpestacin has previously been reported to inhibit syncytium formation during human immunodeficiency virus infection and has been chemically synthesized (11-13). However, neither the molecular target of this compound nor the cellular mechanism of its anti-angiogenic activity has been identified.In the present study we identified the binding protein of terpestacin and...

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“…Interaction with other subunits of the complex is (at least in part) established by the C-termini of subunits VII and VIII. These regions are very hydrophilic, containing many charged residues, and it was proposed that they interact with hydrophilic parts of other subunits [8,37].…”

Section: Discussionmentioning

confidence: 99%

Topological organization of subunits VII and VIII in the ubiquinolcytochrome c oxidoreductase of Saccharomyces cerevisiae

1996

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Based on sensitivity of the protein to proteinase K digestion we now suggest that the N-terminus of subunit VIII is similarly oriented, implying that this subunit does not span the membrane. Despite this, however, subunit VIII cannot be extracted from the membrane even after treatment with 0.1 M Na2CO3 at pH 11.5, showing that the protein is integrally embedded in the membrane. A similar behaviour was displayed by another low molecular weight protein of the complex, subunit VII, which faces the matrix side. A model for the topology of these subunits in the membrane is discussed with respect to the structure of the complex and their involvement in quinone binding.,~?ey words: Membrane topology; Ubiquinol-cytochrome c ~.xidoreductase; Epitope tagging; Integral membrane protein; ( ~accharomyces cerevisiae) tein [8], have shown that at least this part of subunit VIII is exposed to the intermembrane space [9]. In addition, hydrophobicity plots of subunit VIII from S. cerevisiae, K. lactis, S. pombe and the homologous subunit from bovine heart predict the presence of a conserved hydrophobic stretch potentially capable of spanning a lipid bilayer (Fig. 1 and [10]), thus implying that the N-terminus of the protein faces the mitochondrial matrix.In order to verify the accuracy of these predictions, we have tagged the N-terminal half of the protein with two different epitopes (c-myc [11] and HA [12]). As indicated in Fig. I, these epitopes were not placed at the N-terminus of the protein, since the first 25 amino acids may contain a non-cleaved import signal [13]. Using limited protease treatment we have determined the position of the c-myc and the HA epitope with respect to the inner membrane. The outcome of this is combined with carbonate extraction experiments on the entire bca complex in order to further model the topology and subunit arrangement of this large respiratory enzyme.

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The C‐terminus of the 14‐kDa subunit of ubiquinol‐cytochrome‐c oxidoreductase of the yeast Saccharomyces cerevisiae is involved in the assembly of a functional enzyme

Cited by 20 publications

References 39 publications

Identification of additional homologues of subunits VII and VIII of the ubiquinol‐cytochrome c oxidoreductase enables definition of consensus sequences

Identification of additional homologues of subunits VII and VIII of the ubiquinol‐cytochrome c oxidoreductase enables definition of consensus sequences

Terpestacin Inhibits Tumor Angiogenesis by Targeting UQCRB of Mitochondrial Complex III and Suppressing Hypoxia-induced Reactive Oxygen Species Production and Cellular Oxygen Sensing

Topological organization of subunits VII and VIII in the ubiquinolcytochrome c oxidoreductase of Saccharomyces cerevisiae

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