The pentatricopeptide repeat (PPR) is a 35-amino acid sequence motif.
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.
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.
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.