Genes encoding PPR (pentatricopeptide repeat)-containing proteins constitute one of the largest gene families in plants. The majority of these proteins are predicted to target organelles and to bind to RNA. Strikingly, there is a dearth of these proteins in mammals, although genomic searches reveal six candidates, all of which are also predicted to target the mitochondrion. Two of these proteins, POLRMT (the mitochondrial RNA polymerase) and MRPS27, a mitoribosomal protein, are involved in transcription and translation respectively. PTCD1 (pentatricopeptide repeat domain protein 1) and PTCD3 are predicted to be involved in the assembly of respiratory chain complexes, whereas mutations in one other protein, LRPPRC (leucine-rich pentatricopeptide repeat cassette), have been shown to cause defects in the levels of cytochrome c oxidase, the terminal member of the respiratory chain. In this issue of the Biochemical Journal, Xu et al. turn their attention to the remaining candidate, PTCD2. Depletion in a mouse model led to deficiencies of the third complex of the respiratory chain that caused profound ultrastructural changes in the heart. The exact molecular function of PTCD2 remains unclear, but depletion leads to an apparent lack of processing of the mitochondrial transcript encoding apocytochrome b, a critical member of complex III. These data are consistent with PTCD2 playing an important role in the post-transcriptional expression of the mitochondrial genome.
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October 28 2008
PPR (pentatricopeptide repeat) proteins in mammals: important aids to mitochondrial gene expression
Robert N. Lightowlers;
Robert N. Lightowlers
1
1Mitochondrial Research Group, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, U.K.
1To whom correspondence should be addressed (email R.N.Lightowlers@ncl.ac.uk).
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Zofia M. A. Chrzanowska-Lightowlers
Zofia M. A. Chrzanowska-Lightowlers
1Mitochondrial Research Group, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, U.K.
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Publisher: Portland Press Ltd
Received:
September 25 2008
Accepted:
September 26 2008
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem J (2008) 416 (1): e5–e6.
Article history
Received:
September 25 2008
Accepted:
September 26 2008
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Citation
Robert N. Lightowlers, Zofia M. A. Chrzanowska-Lightowlers; PPR (pentatricopeptide repeat) proteins in mammals: important aids to mitochondrial gene expression. Biochem J 15 November 2008; 416 (1): e5–e6. doi: https://doi.org/10.1042/BJ20081942
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