RNase P without RNA: identification and functional reconstitution of the human mitochondrial tRNA processing enzyme

Cell. 2008 Oct 31;135(3):462-74. doi: 10.1016/j.cell.2008.09.013.


tRNAs are synthesized as immature precursors, and on their way to functional maturity, extra nucleotides at their 5' ends are removed by an endonuclease called RNase P. All RNase P enzymes characterized so far are composed of an RNA plus one or more proteins, and tRNA 5' end maturation is considered a universal ribozyme-catalyzed process. Using a combinatorial purification/proteomics approach, we identified the components of human mitochondrial RNase P and reconstituted the enzymatic activity from three recombinant proteins. We thereby demonstrate that human mitochondrial RNase P is a protein enzyme that does not require a trans-acting RNA component for catalysis. Moreover, the mitochondrial enzyme turns out to be an unexpected type of patchwork enzyme, composed of a tRNA methyltransferase, a short-chain dehydrogenase/reductase-family member, and a protein of hitherto unknown functional and evolutionary origin, possibly representing the enzyme's metallonuclease moiety. Apparently, animal mitochondria lost the seemingly ubiquitous RNA world remnant after reinventing RNase P from preexisting components.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Evolution, Molecular
  • Female
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mitochondria / enzymology*
  • RNA, Catalytic / analysis*
  • RNA, Transfer / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ribonuclease P / chemistry*
  • Ribonuclease P / genetics
  • Ribonuclease P / isolation & purification
  • Ribonuclease P / metabolism


  • RNA, Catalytic
  • Recombinant Proteins
  • RNA, Transfer
  • Ribonuclease P