A single Arabidopsis organellar protein has RNase P activity

Abstract

The ubiquitous endonuclease RNase P is responsible for the 5' maturation of tRNA precursors. Until the discovery of human mitochondrial RNase P, these enzymes had typically been found to be ribonucleoproteins, the catalytic activity of which is associated with the RNA component. Here we show that, in Arabidopsis thaliana mitochondria and plastids, a single protein called 'proteinaceous RNase P' (PRORP1) can perform the endonucleolytic maturation of tRNA precursors that defines RNase P activity. In addition, PRORP1 is able to cleave tRNA-like structures involved in the maturation of plant mitochondrial mRNAs. Finally, we show that Arabidopsis PRORP1 can replace the bacterial ribonucleoprotein RNase P in Escherichia coli cells. PRORP2 and PRORP3, two paralogs of PRORP1, are both localized in the nucleus.

Ribonucleases P/MRP and the Expanding Ribonucleoprotein World

“…Given the substrate promiscuity of RNA-based nuclear RNase P (Tables 1 and 3), it is surprising that a new, multicomponent complex had to be recruited for this function. An MRPP3 homologous, nuclear-encoded, component located in mitochondria and chloroplasts with RNase P activity (PRORP1) was found in Arabidopsis thaliana (93) and in an unknown location in Ostreococcus tauri (95). This finding represents an example of a relatively recent evolutionary event where RNA function may have been replaced by a showing the general distribution of the protein subunits of RNases P/MRP in the three domains of life.…”

Downward causation by information control in micro-organisms

“…coli where the RNase P function, which is essentially based on an RNA in bacteria, is replaced by a purely proteinaceous RNase P from plant organelles [24]. By substituting a function carried by an RNA with one carried by a protein, one cannot argue that the two molecular systems are swappable simply because they share conserved structural features.…”

“…The complementation experiments involving functions carried out by amino-acyl tRNA synthetases (aaRS) [22,23] (figure 3d ), RNase P [24], flippases [52] and pyrophosphatases [53] demonstrate without ambiguity that very different modes of molecular operations could be substituted by one another as long as their function remains the same (table 1 and figure 5). In all cases, the molecular instructions that are exchanged have likely originated by ultimate convergent evolution [41,42] because they do not share any apparent structural similarities.…”

“…By substituting a function carried by an RNA with one carried by a protein, one cannot argue that the two molecular systems are swappable simply because they share conserved structural features. In this experiment and others [22][23][24]52,53], the only feature that the exchanged molecular systems share is their functional outcome. These experiments are therefore in much stronger support of TDC than that [25] originally mentioned by Auletta et al [12].…”

“…They establish in vivo the existence of various classes of functional equivalence within the OS genetic network [22][23][24] and the metabolic networks [52,53] in bacteria, archaea and lower eukaryotes (e.g. yeast [53]).…”