Pentatricopeptide repeat (PPR) proteins constitute a large family of RNA-binding proteins that contain a canonical 35 residue repeat motif. Seven examples have been identified in human mitochondria, and are known to affect mitochondrial translation [, ]. One of these is PTCD2, a pentatricopeptide domain (PTCD)-containing protein that affects mitochondrial translation. PTCD2 appears to have a role in processing RNA transcripts involving cytochrome b encoded by mitochondrial DNA []. Disruption in PTCD2 resulted in elevated levels of the unprocessed precursor encoding cytochrome b. PTCD2 has been identified as a target for autoantibodies in neurodegenerative disease and is used as a biomarker for Alzheimer disease [].
Mammalian pentatricopeptide repeat domain (PPR) proteins are involved in regulation of mitochondrial RNA metabolism and translation and are required for mitochondrial function. The supernumerary mitochondrial ribosomal protein of the small subunit 27 (MRPS27) is not required for mitochondrial RNA processing or the stability of the small ribosomal subunit. However, MRPS27 is required for mitochondrial protein synthesis [].Pentatricopeptide repeat-containing protein 2 (PTCD2) is a related mitochondrial PPR protein, although despite their similarity, they may not have the same function [, ]. PTCD2 has a role in mitochondrial RNA metabolism and downstream effects on mitochondrial translation [, ]. PTCD2 has been identified as a target for autoantibodies in neurodegenerative disease and is used as a biomarker for Alzheimer disease [].
