title: RNase P without RNA: identification and functional reconstitution of the human mitochondrial tRNA processing enzyme.
abstract: 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.
authors.affiliation: Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria.
authors.forename: Johann
authors.initials: J
authors.lastname: Holzmann
authors.forename: Peter
authors.initials: P
authors.lastname: Frank
authors.forename: Esther
authors.initials: E
authors.lastname: Löffler
authors.forename: Keiryn L
authors.initials: KL
authors.lastname: Bennett
authors.forename: Christopher
authors.initials: C
authors.lastname: Gerner
authors.forename: Walter
authors.initials: W
authors.lastname: Rossmanith
mesh_terms: D000818:Animals; D002460:Cell Line; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000201:enzymology*; D016337:RNA, Catalytic / Q000032:analysis*; D012343:RNA, Transfer / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D043262:Ribonuclease P / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D016337:RNA, Catalytic; D011994:Recombinant Proteins; D012343:RNA, Transfer; D043262:Ribonuclease P