Pentatricopeptide repeat | |||||||||
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Identifiers | |||||||||
Symbol | PPR | ||||||||
Pfam | PF01535 | ||||||||
Pfam clan | CL0020 | ||||||||
InterPro | IPR002885 | ||||||||
PROSITE | PS51375 | ||||||||
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The pentatricopeptide repeat (PPR) is a 35-amino acid sequence motif. Pentatricopeptide-repeat-containing proteins are a family of proteins commonly found in the plant kingdom. They are distinguished by the presence of tandem degenerate PPR motifs [1] and by the relative lack of introns in the genes coding for them. [2]
Approximately 450 such proteins have been identified in the Arabidopsis genome, and another 477 in the rice genome. [3] Despite the large size of the protein family, genetic data suggest that there is little or no redundancy of function between the PPR proteins in Arabidopsis. [2]
The purpose of PPR proteins is currently under dispute. It has been shown that a good deal of those in Arabidopsis interact (often essentially) with mitochondria and other organelles [2] and that they are possibly involved in RNA editing. [4] However many trans proteins are required for this editing to occur and research continues to look at which proteins are needed. [5]
The structure of the PPR has been resolved. It folds into a helix-turn-helix structure similar to those found in the tetratricopeptide repeat. Several repeats of the protein forms a ring around a single-strand RNA molecule in a sequence-sensitive way reminiscent of TAL effectors. [6]
Human genes encoding proteins containing this repeat include:
Symbiogenesis is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes taken one inside the other in endosymbiosis. Mitochondria appear to be phylogenetically related to Rickettsiales bacteria, while chloroplasts are thought to be related to cyanobacteria.
RNA editing is a molecular process through which some cells can make discrete changes to specific nucleotide sequences within an RNA molecule after it has been generated by RNA polymerase. It occurs in all living organisms and is one of the most evolutionarily conserved properties of RNAs. RNA editing may include the insertion, deletion, and base substitution of nucleotides within the RNA molecule. RNA editing is relatively rare, with common forms of RNA processing not usually considered as editing. It can affect the activity, localization as well as stability of RNAs, and has been linked with human diseases.
F-box proteins are proteins containing at least one F-box domain. The first identified F-box protein is one of three components of the SCF complex, which mediates ubiquitination of proteins targeted for degradation by the 26S proteasome.
In molecular biology, snoRNA U34 is a non-coding RNA (ncRNA) molecule which functions in the modification of other small nuclear RNAs (snRNAs). This type of modifying RNA is usually located in the nucleolus of the eukaryotic cell which is a major site of snRNA biogenesis. It is known as a small nucleolar RNA (snoRNA) and also often referred to as a guide RNA.
CUG triplet repeat, RNA binding protein 1, also known as CUGBP1, is a protein which in humans is encoded by the CUGBP1 gene.
CUGBP, Elav-like family member 2, also known as Etr-3 is a protein that in humans is encoded by the CELF2 gene.
Transcription elongation regulator 1, also known as TCERG1, is a protein which in humans is encoded by the TCERG1 gene.
40S ribosomal protein S16' is a protein that in humans is encoded by the RPS16 gene.
60S ribosomal protein L14 is a protein that in humans is encoded by the RPL14 gene.
60S ribosomal protein L12 is a protein that in humans is encoded by the RPL12 gene.
60S ribosomal protein L28 is a protein that in humans is encoded by the RPL28 gene.
60S ribosomal protein L13a is a protein that in humans is encoded by the RPL13A gene.
Leucine-rich PPR motif-containing protein, mitochondrial is a protein that in humans is encoded by the LRPPRC gene. Transcripts ranging in size from 4.8 to 7.0 kb which result from alternative polyadenylation have been reported for this gene.
40S ribosomal protein S8 is a protein that in humans is encoded by the RPS8 gene.
Pleiotropic regulator 1 is a protein that in humans is encoded by the PLRG1 gene.
60S ribosomal protein L37 is a protein that in humans is encoded by the RPL37 gene.
Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nucleus. The existence of chloroplast DNA was identified biochemically in 1959, and confirmed by electron microscopy in 1962. The discoveries that the chloroplast contains ribosomes and performs protein synthesis revealed that the chloroplast is genetically semi-autonomous. The first complete chloroplast genome sequences were published in 1986, Nicotiana tabacum (tobacco) by Sugiura and colleagues and Marchantia polymorpha (liverwort) by Ozeki et al. Since then, a great number of chloroplast DNAs from various species have been sequenced.
Alice Barkan is an American molecular biologist and a professor of biology at the University of Oregon. She is known for her work on chloroplast gene regulation and protein synthesis.
Jian-Kang Zhu is a plant scientist, researcher and academic. He is a Senior Principal Investigator in the Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences (CAS). He is also the Academic Director of CAS Center of Excellence in Plant Sciences.
Maureen Hanson is an American molecular biologist and Liberty Hyde Bailey Professor in the Department of Molecular Biology and Genetics at Cornell University in Ithaca, New York. She is a joint member of the Section of Plant Biology and Director of the Center for Enervating Neuroimmune Disease. Her research concerns gene expression in chloroplasts and mitochondria, photosynthesis, and the molecular basis of the disease Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).