This repeat has no known function. It is about 35 amino acids long and found in up to 18 copies in some proteins. This family appears to be greatly expanded in plants. This repeat occurs in PET309 Swiss:P32522 that may be involved in RNA stabilisation [1]. This domain occurs in crp1 that is involved in RNA processing [2]. This repeat is associated with a predicted plant protein Swiss:O49549 that has a domain organisation similar to the human BRCA1 protein. The repeat has been called PPR [3].

1: 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. Manthey GM, McEwen JE; EMBO J 1995;14:4031-4043. PMID:7664742

2: 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. Barkan A, Walker M, Nolasco M, Johnson D; EMBO J 1994;13:3170-3181. PMID:8039510

3: The PPR motif - a TPR-related motif prevalent in plant organellar proteins. Small ID, Peeters I; Trends Biochem Sci 2000;25:45-47. PMID:10664580