{{Pfam_box | Symbol = PPR | Name = Pentatricopeptide repeat | image = | width = | caption = | Pfam= PF01535 | Pfam_clan = CL0020 | InterPro= IPR002885 | SMART= | Prosite = PS51375 | SCOP = | TCDB = | OPM family= | OPM protein= | PDB= }}
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<ref name="pmid16837079">{{cite journal |vauthors=Mingler MK, Hingst AM, Clement SL, Yu LE, Reifur L, Koslowsky DJ | title = Identification of pentatricopeptide repeat proteins in Trypanosoma brucei | journal = Mol. Biochem. Parasitol. | volume = 150 | issue = 1 | pages = 37–45 |date=November 2006 | pmid = 16837079 | doi = 10.1016/j.molbiopara.2006.06.006 }}</ref> and by the relative lack of introns in the genes coding for them.<ref name="pmid15269332"/>
Approximately 450 such proteins have been identified in the Arabidopsis genome, and another 477 in the rice genome.<ref name="pmid18343892">{{cite journal |vauthors=O'Toole N, Hattori M, Andres C, Iida K, Lurin C, Schmitz-Linneweber C, Sugita M, Small I | title = On the expansion of the pentatricopeptide repeat gene family in plants | journal = Mol. Biol. Evol. | volume = 25 | issue = 6 | pages = 1120–8 |date=June 2008 | pmid = 18343892 | doi = 10.1093/molbev/msn057 | doi-access = free }}</ref> 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''.<ref name="pmid15269332"/>
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<ref name="pmid15269332">{{cite journal |vauthors=Lurin C, Andrés C, Aubourg S, Bellaoui M, Bitton F, Bruyère C, Caboche M, Debast C, Gualberto J, Hoffmann B, Lecharny A, Le Ret M, Martin-Magniette ML, Mireau H, Peeters N, Renou JP, Szurek B, Taconnat L, Small I | title = Genome-wide analysis of Arabidopsis pentatricopeptide repeat proteins reveals their essential role in organelle biogenesis | journal = Plant Cell | volume = 16 | issue = 8 | pages = 2089–103 |date=August 2004 | pmid = 15269332 | pmc = 519200 | doi = 10.1105/tpc.104.022236 }}</ref> and that they are possibly involved in RNA editing.<ref name="pmid15662426">{{cite journal |vauthors=Kotera E, Tasaka M, Shikanai T | title = A pentatricopeptide repeat protein is essential for RNA editing in chloroplasts | journal = Nature | volume = 433 | issue = 7023 | pages = 326–30 |date=January 2005 | pmid = 15662426 | doi = 10.1038/nature03229 | bibcode = 2005Natur.433..326K | s2cid = 4416316 }}</ref> However many trans proteins are required for this editing to occur and research continues to look at which proteins are needed.<ref name="pmid20566637">{{cite journal |vauthors=Takenaka M, Verbitskiy D, Zehrmann A, Brennicke A | title = Reverse genetic screening identifies five E-class PPR-proteins involved in RNA editing in mitochondria of Arabidopsis Thaliana | journal = J Biol Chem | volume = 285| issue = 35| pages = 27122–27129|date=June 2010 | pmid = 20566637 | doi = 10.1074/jbc.M110.128611 | doi-access = free | pmc = 2930711 }}</ref>
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.<ref name="pmid24162847">{{cite journal | vauthors = Yin P, Li Q, Yan C, Liu Y, Liu J, Yu F, Wang Z, Long J, He J, Wang HW, Wang J, Zhu JK, Shi Y, Yan N | display-authors = 6 | title = Structural basis for the modular recognition of single-stranded RNA by PPR proteins | journal = Nature | volume = 504 | issue = 7478 | pages = 168–71 | date = December 2013 | pmid = 24162847 | doi = 10.1038/nature12651 | bibcode = 2013Natur.504..168Y | s2cid = 4471801 }}</ref>
== Examples ==
Human genes encoding proteins containing this repeat include: * DENND4A, DENND4B, DENND4C * LRPPRC * PTCD1, PTCD2, PTCD3 * MRPS27
== References == {{reflist}}
Category:Amino acid motifs
{{molecular-biology-stub}}