Abstract
The pentatricopeptide repeat (PPR) proteins organize a super family only in higher plant species (450 proteins in A. thaliana, less than 10 in other eukaryotes, none in prokaryotes and archaeas). They are predicted to be involved in RNA/DNA metabolism in chloroplast or mitochondria.
A nuclear-encoded HCF152 has primarily 12 PPR motifs. The non-photosynthetic mutant of Arabidopsis HCF152 impaired the processing of the chloroplast polycistronic transcript from psbB-psbT-psbH-petB-petD.
It was found that two HCF152 bind to form a homodimer. The recombinant HCF152 bound the petB exon-introns junctions with higher affinity. When truncated proteins composed of different numbers of PPR motifs were analyzed, it was found that at least two PPR motifs were necessary for RNA-binding. The affinity to RNA increased progressively with numbers of PPR motifs. We discuss the possible role of the PPR protein super-family in organelle RNA metabolism.
