RNase P without RNA: Identification and Functional Reconstitution of the Human Mitochondrial tRNA Processing Enzyme

• Published in: Cell 2008-10, Vol.135 (3), p.462-474
• Main Authors: Holzmann, Johann, Frank, Peter, Löffler, Esther, Bennett, Keiryn L., Gerner, Christopher, Rossmanith, Walter
• Format: Article
• Language: English
• Subjects: Animals; Cell Line; Escherichia coli - genetics; Escherichia coli - metabolism; Evolution, Molecular; Female; Humans; Male; Mice; Mice, Inbred C57BL; Mitochondria - enzymology; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Ribonuclease P - chemistry; Ribonuclease P - genetics; Ribonuclease P - isolation & purification; Ribonuclease P - metabolism; RNA; RNA, Catalytic - analysis; RNA, Transfer - metabolism
• ISSN: 0092-8674; 1097-4172
• 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.