| 1. |
- Asin-Cayuela, Jorge, et al.
(author)
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The human mitochondrial transcription termination factor (mTERF) is fully active in vitro in the non-phosphorylated form.
- 2005
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In: The Journal of biological chemistry. - 0021-9258. ; 280:27, s. 25499-505
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Journal article (peer-reviewed)abstract
- The human mitochondrial transcription termination factor (mTERF) is a 39-kDa protein that terminates transcription at the 3'-end of the 16 S rRNA gene and thereby controls expression of the ribosomal transcription unit of mitochondrial DNA. The transcription termination activity of human mTERF has been notoriously difficult to study in vitro, and it has been suggested that the activity of the protein is regulated by posttranslational modifications or by protein polymerization. We here characterize the activity of recombinant human mTERF expressed in insect cells. We observed that mTERF efficiently promotes sequence-specific termination in a completely recombinant and highly purified in vitro system for mitochondrial transcription. The termination activity has a distinct polarity, and we observed complete transcription termination when the mTERF-binding site is oriented in a forward position relative the heavy strand promoter but only partial transcription termination when the binding site is in the reverse position. We analyzed the biochemical characteristics of the active mTERF protein and found that it is a stable monomer at physiological salt concentration. Structural analysis, including phosphostaining, two-dimensional electrophoresis, and electrospray mass spectrometry, detected no evidence of phosphorylation. We conclude that the monomeric human mTERF is fully active in its non-phosphorylated form and that the protein does not require additional cellular factors to terminate mitochondrial transcription in vitro.
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| 2. |
- Cochemé, Helena M, et al.
(author)
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Mitochondrial targeting of quinones: therapeutic implications.
- 2007
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In: Mitochondrion. - : Elsevier BV. - 1567-7249. ; 7 Suppl
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Research review (peer-reviewed)abstract
- Mitochondrial oxidative damage contributes to a range of degenerative diseases. Ubiquinones have been shown to protect mitochondria from oxidative damage, but only a small proportion of externally administered ubiquinone is taken up by mitochondria. Conjugation of the lipophilic triphenylphosphonium cation to a ubiquinone moiety has produced a compound, MitoQ, which accumulates selectively into mitochondria. MitoQ passes easily through all biological membranes and, because of its positive charge, is accumulated several hundred-fold within mitochondria driven by the mitochondrial membrane potential. MitoQ protects mitochondria against oxidative damage in vitro and following oral delivery, and may therefore form the basis for mitochondria-protective therapies.
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| 3. |
- Pellegrini, Mina, et al.
(author)
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MTERF2 is a nucleoid component in mammalian mitochondria.
- 2009
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In: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2728. ; 1787:5, s. 296-302
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Journal article (peer-reviewed)abstract
- The mammalian MTERF family of proteins has four members, named MTERF1 to MTERF4, which were identified in homology searches using the mitochondrial transcription termination factor, mTERF (here denoted MTERF1) as query. MTERF1 and MTERF3 are known to participate in the control of mitochondrial DNA transcription, but the function of the other two proteins is not known. We here investigate the structure and function of MTERF2. Protein import experiments using isolated organelles confirm that MTERF2 is a mitochondrial protein. Edman degradation of MTERF2 isolated from stably transfected HeLa cells demonstrates that mature MTERF2 lacks a targeting peptide (amino acids 1-35) present in the precursor form of the protein. MTERF2 is a monomer in isolation and displays a non sequence-specific DNA-binding activity. In vivo quantification experiments demonstrate that MTERF2 is relatively abundant, with one monomer present per approximately 265 bp of mtDNA. In comparison, the mtDNA packaging factor TFAM is present at a ratio of one molecule per approximately 10-12 bp of mtDNA. Using formaldehyde cross-linking we demonstrate that MTERF2 is present in nucleoids, and therefore must be located in close proximity to mtDNA. Taken together, our work provides a basic biochemical characterization of MTERF2, paving the way for future functional studies.
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