Abstract
RNase P, the essential activity that performs the 5′ maturation of tRNA precursors, can be achieved either by ribonucleoproteins containing a ribozyme present in the three domains of life or by protein-only enzymes called protein-only RNase P (PRORP) that occur in eukaryote nuclei and organelles. A fast growing list of studies has investigated three-dimensional structures and mode of action of PRORP proteins. Results suggest that similar to ribozymes, PRORP proteins have two main domains. A clear functional analogy can be drawn between the specificity domain of the RNase P ribozyme and PRORP pentatricopeptide repeat domain, and between the ribozyme catalytic domain and PRORP N4BP1, YacP-like Nuclease domain. Moreover, both types of enzymes appear to dock with the acceptor arm of tRNA precursors and make specific contacts with the corner of pre-tRNAs. While some clear differences can still be delineated between PRORP and ribonucleoprotein (RNP) RNase P, the two types of enzymes seem to use, fundamentally, the same catalytic mechanism involving two metal ions. The occurrence of PRORP and RNP RNase P represents a remarkable example of convergent evolution. It might be the unique witness of an ongoing replacement of catalytic RNAs by proteins for enzymatic activities.
Highlights
Similar to Janus, the two-faced Roman god of transitions and passages that concomitantly looks to the future and to the past, RNase P has two faces
It was predicted that separate PPR motifs of protein-only RNase P (PRORP) might interact with individual residues in the T and/or D loops of pre-tRNAs [5,56,58]
Probably interact with the Watson-Crick side of residues, such as C56, R57, or G18. This would, in turn, imply that pre-tRNA substrates recognized by PRORP are not stabilized by Watson-Crick interactions that occur in mature tRNAs, i.e., the C56-G19 interaction or the G18-Ψ55 interaction
Summary
Similar to Janus, the two-faced Roman god of transitions and passages that concomitantly looks to the future and to the past, RNase P has two faces This essential enzymatic activity that removes the 51 leader sequences of tRNA precursors occurs either as ribonucleoproteins (RNP) involving a ribozyme [1] or as protein-only enzymes [2,3,4,5]. RNP RNases P are present in all three domains of life, their catalytic RNA (P RNA) structure is relatively well conserved in prokaryotes and eukaryote nuclei [10]. It is highly degenerate in several organelles [12]. RNase P and discuss how PRORP structure, pre-tRNA recognition, and cleavage differ, and resemble that of RNP RNase P
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