PPR repeatThis 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 that may be involved in RNA stabilisation. This domain occurs in crp1 that is involved in RNA processing. This repeat is associated with a predicted plant protein that has a domain organisation similar to the human BRCA1 protein. The repeat has been called PPR.