A Pentatricopeptide Repeat Protein in the Plasmodium apicoplast is essential and shows sequence-specific RNA binding

The malaria parasite Plasmodium and other apicomplexans such as Toxoplasma evolved from photosynthetic organisms and contain an essential, remnant plastid termed the apicoplast. Transcription of the apicoplast genome is polycistronic with extensive RNA processing. Little is known about the mechanism of post-transcriptional processing. In plant chloroplasts, post-transcriptional RNA processing is controlled by multiple pentatricopeptide repeat (PPR) proteins. Here, we present the biochemical characterisation of the single apicoplast-targeted PPR protein. Apicoplast PPR1 is essential, and binds specific RNA sequences corresponding with previously characterized RNA processing sites. We identify the specific binding motif of PPR1. In RNAse protection assays, PPR1 shields apicoplast transcripts from ribonuclease degradation. Our results show that apicoplast RNA processing is under the control of a single protein, thus presenting an Achilles heel for the development of new anti-malarial drugs.