Abstract
The expression of organellar genes is extensively regulated by nuclear-encoded factors via post-transcriptional events, such as RNA cleavage, editing, stabilization and translation. Recently, the pentatricopeptide repeat (PPR) proteins, a large protein family expanded only in higher plants, have been proposed to play pivotal roles in these regulations. PPR proteins, typically, consist of tandem arrays of PPR motifs, and are involved in various post-transcriptional events by interacting one specific RNA or a small subset of RNAs, although the PPR motifs themselves displays no activity for RNA catalysis. Therefore, the PPR proteins may act as adaptors, recognizing specific RNA and facilitating interactions with processing enzymes. The recognition of specific RNA sequence is speculated to be depended the variety and/or combination of PPR motifs, although the mechanisms are fully unknown. Here, we analyzed the RNA binding properties of full-length and truncated versions of several PPR proteins, whose target RNA molecules have been identified. The mutagenesis study based on the structural modeling of PPR protein, revealed several amino acids to be involved in the RNA interaction.
