This entry represents the PPR repeat.
Pentatricopeptide repeat (PPR) proteins are characterised by tandem repeats of a degenerate 35 amino acid motif [1]. Most of PPR proteins have roles in mitochondria or plastid [2]. PPR repeats were discovered while screening Arabidopsis proteins for those predicted to be targeted to mitochondria or chloroplast [3, 3]. Some of these proteins have been shown to play a role in post-transcriptional processes within organelles and they are thought to be sequence-specific RNA-binding proteins [4, 5, 6]. Plant genomes have between one hundred to five hundred PPR genes per genome whereas non-plant genomes encode two to six PPR proteins.
Although no PPR structures are yet known, the motif is predicted to fold into a helix-turn-helix structure similar to those found in the tetratricopeptide repeat (TPR) family (see PDOC50005) [7].
The plant PPR protein family has been divided in two subfamilies on the basis of their motif content and organisation [7, 7].
Examples of PPR repeat-containing proteins include PET309 P32522, which may be involved in RNA stabilisation [8], and crp1, which is involved in RNA processing [9]. The repeat is associated with a predicted plant protein O49549 that has a domain organisation similar to the human BRCA1 protein.
1. The PPR motif - a TPR-related motif prevalent in plant organellar proteins. Trends Biochem. Sci. 25, 46-7
2. Chloroplast RNA-binding and pentatricopeptide repeat proteins. Biochem. Soc. Trans. 32, 571-4
3. Genome-wide analysis of Arabidopsis pentatricopeptide repeat proteins reveals their essential role in organelle biogenesis. Plant Cell 16, 2089-103
4. HCF152, an Arabidopsis RNA binding pentatricopeptide repeat protein involved in the processing of chloroplast psbB-psbT-psbH-petB-petD RNAs. Plant Cell 15, 1480-95
5. LRP130, a pentatricopeptide motif protein with a noncanonical RNA-binding domain, is bound in vivo to mitochondrial and nuclear RNAs. Mol. Cell. Biol. 23, 4972-82
6. Pentatricopeptide repeat (PPR) proteins as sequence-specificity factors in post-transcriptional processes in organelles. Biochem. Soc. Trans. 35, 1643-7
7. Pentatricopeptide repeat proteins and their emerging roles in plants. Plant Physiol. Biochem. 45, 521-34
8. The product of the nuclear gene PET309 is required for translation of mature mRNA and stability or production of intron-containing RNAs derived from the mitochondrial COX1 locus of Saccharomyces cerevisiae. EMBO J. 14, 4031-43
9. A nuclear mutation in maize blocks the processing and translation of several chloroplast mRNAs and provides evidence for the differential translation of alternative mRNA forms. EMBO J. 13, 3170-81
Show less...
Expansion plot
Gene family finder
Synteny plot
Ks-graphs
Skyline plot
WGDotplot
Functional clusters
WGMapping
BLAST
Workbench