Archaeal RNase P

Ribonuclease P (RNase P) is a ubiquitous endoribonuclease, found in archaea, bacteria, and eukarya, as well as chloroplasts and mitochondria. Its best characterized activity is the generation of mature 5'-ends of tRNAs by cleaving the 5'-leader elements of precursor-tRNAs. Cellular RNase Ps are ribonucleoproteins. RNA from bacterial RNase Ps retains its catalytic activity in the absence of the protein subunit, i.e. it is a ribozyme. Isolated eukaryotic and archaeal RNase P RNA has not been shown to retain its catalytic function, but is still essential for the catalytic activity of the holoenzyme. Although the archaeal and eukaryotic holoenzymes have a much greater protein content than the bacterial ones, the RNA cores from all the three lineages are homologous -- helices corresponding to P1, P2, P3, P4, and P10/11 are common to all cellular RNase P RNAs. Yet, there is considerable sequence variation, particularly among the eukaryotic RNAs.