Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.26.5 (RNase P)
1,348 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After purification from extracts of whole cells, M1 RNA, the catalytic subunit of ribonuclease P from Escherichia coli, apparently must undergo a change in conformation before it can function catalytically. The rate of this conformational change is dependent upon the duration of incubation at various temperatures and pH. delta E of the transition at pH 7.5 is approximately 36 kcal/mol. The change in conformation is not sensitive to Mg2+ concentration between 10 and 100 mM. A decrease in A260 of M1 RNA in solution has been observed during the incubation period that potentiates the conformational change at 30 degrees C, but no direct correlation can yet be made to specific structural rearrangements.
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PMID:M1 RNA, the RNA subunit of Escherichia coli ribonuclease P, can undergo a pH-sensitive conformational change. 242 64

The RNA moiety of ribonuclease P from Escherichia coli (M1 RNA) has been photoreacted with 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) and long-wave UV light (320-380 nm) in a buffer containing 60 mM Mg2+, where the RNA moiety acts as a true catalyst of tRNA processing. Limited specific digestion and two-dimensional gel electrophoresis yield fragments cross-linked by HMT. By photoreversal of the isolated cross-linked fragments and enzymatic sequencing of the fragments, the positions of the cross-links have been elucidated. This method allows us to locate the cross-link to +/- 15 nucleotides. Further assignments of the exact locations of the cross-links have been made on the basis of the known photoreactivity of the psoralen with different bases. Nine unique cross-links have been isolated in the M1 RNA including four long-range interactions. The short-range interactions are discussed here in detail.
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PMID:Structure of M1 RNA as determined by psoralen cross-linking. 245 May 74

We have constructed a plasmid expressing E. coli M1 RNA, the catalytic RNA subunit of ribonuclease P, under the control of a phage T7 promoter. The active M1 RNA species synthesized in vitro by T7 RNA polymerase from this vector was reacted with the tRNA(Gln) - tRNA(Leu) precursor RNA (Band K) encoded by phage T4. Only the tRNA(Leu) moiety of this dimeric precursor RNA contains the 3' terminal C-C-A sequence common to all tRNAs. We observed that protein-free M1 RNA was capable of processing the precursor RNA at the 5' ends of both tRNA tRNA sequences. The rate of cleavage of the tRNA(Gln) sequence was more strongly dependent on [Mg2+] than that of tRNA(Leu), increasing severalfold between 100 and 500 mM Mg2+, conditions under which the rate of cleavage at the tRNA(Leu) sequence was constant.
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PMID:Dependence of M1 RNA substrate specificity on magnesium ion concentration. 245 26

The leuX gene of Escherichia coli codes for a suppressor tRNA and forms a single gene operon containing its own promoter and Q-independent terminator. An analysis of the in vitro processing of leuX precursor revealed that the processing of the 5' end took place in a single-step reaction catalysed by RNase P while the 3' processing involved two successive reactions. The endonucleolytic cleavage activity of the 3' precursor sequence was found to copurify with RNase P. Heat inactivation of thermosensitive RNase P from two independent E. coli mutants abolished the cleavage activity of both the 5' and 3' ends. These results altogether suggest that RNase P carries the activity of 3' end cleavage as well as that of 5' processing. In the presence of Mg2+ alone, the leuX precursor was found to be self-cleaved at a site approximately 13 nt inside from the 5' end of mature tRNA. The self-cleaved precursor tRNA was no longer processed by the 3' endonuclease, suggesting that the 3' endonuclease recognizes a specific conformation of the precursor tRNA for action.
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PMID:A novel function of RNase P from Escherichia coli: processing of a suppressor tRNA precursor. 306 98

RNAase P (EC 3.1.26.5) activity has been identified in chick embryo thigh tissue on the basis of specific cleavage of Escherichia coli 129 nucleotide tRNATyr precursor and has been partially purified by the procedure used for human tissue culture KB cell RNAase P. RNAase P from chick resembles the KB cell RNAase P in substrate specificity, requirement for a divalent cation (Mg2+) and a monovalent cation (K+, Na+ or NH4+) for activity, inhibition by bulk tRNA, ready inactivation by proteases, and increasing instability; with purification. RNAase P activity is also present in whole chick embryos, as well as in liver and heart tissues. Furthermore, crude preparations of RNAase P from chick embryo heart tissue are relatively free of contaminating nucleases.
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PMID:Identification of ribonuclease P activity from chick embryos. 616 Aug 76

The RNA moieties of ribonuclease P purified from both E. coli (M1 RNA) and B. subtilis (P-RNA) can cleave tRNA precursor molecules in buffers containing either 60 mM Mg2+ or 10 mM Mg2+ plus 1 mM spermidine. The RNA acts as a true catalyst under these conditions whereas the protein moieties of the enzymes alone show no catalytic activity. However, in buffers containing 5-10 mM Mg2+ (in the absence of spermidine) both kinds of subunits are required for enzymatic activity, as shown previously. In the presence of low concentrations of Mg2+, in vitro, the RNA and protein subunits from one species can complement subunits from the other species in reconstitution experiments. When the precursor to E. coli 4.5S RNA is used as a substrate, only the enzyme complexes formed with M1 RNA from E. coli and the protein moieties from either bacterial species are active.
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PMID:The RNA moiety of ribonuclease P is the catalytic subunit of the enzyme. 619 86

Ribonuclease P, which contains a catalytic RNA subunit, cleaves 5' precursor-specific sequences from pre-tRNAs. It was previously shown that the RNase P RNA optimally cleaves substrates which contain the mature, 3'-terminal CCA of tRNA. In order to determine the contributions of those individual 3'-terminal nucleotides to the interaction, pre-tRNAs that have CCA, only CC or C or are without CCA at the 3'-end were synthesized by run-off transcription, tested as substrates for cleavage by RNase P RNA and used in photoaffinity crosslinking experiments to examine contact sites in the ribozyme. In order to generalize the results, analyses were carried out using three different bacterial RNase P RNAs, from Escherichia coli, Bacillus subtilis and Thermotoga maritima. At optimal (Kcat/Km) ionic strength (1 M NH4+/25 mM Mg2+), Km increases incrementally 3- to 10-fold upon stepwise removal of each nucleotide from the 3'-end. At high ionic strength (2 M NH4+/50 mM Mg2+), which suppresses conformational effects, removal of the 3'-terminal A had little effect on Km, indicating that it is not a specific contact. Analysis of the deletion and substitution mutants indicated that the C residues act specially; their contribution to binding energy at high ionic strength (approximately 1 kcal/mol) is consistent with a non-Watson-Crick interaction, possibly irregular triple-strand formation with some component of the RNase P RNA. In agreement with previous studies, we find that the RNase P holoenzyme in vitro does not discriminate between tRNAs containing or lacking CCA. The structural elements of the three RNase P RNAs in proximity to the 3'-end of tRNA were examined by photoaffinity crosslinking. Photoagent-labeled tRNAs with 3'-terminal CCA, only CC or C, or lacking all these nucleotides were covalently conjugated to the three RNase P RNAs by irradiation and the sites of crosslinks were mapped by primer extension. The main crosslink sites are located in a highly conserved loop (probably an irregular helix) that is part of the core of the RNase P RNA secondary structure. The crosslinking results orient the CCA of tRNA with respect to that region of the RNase P RNA.
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PMID:Interaction of the 3'-end of tRNA with ribonuclease P RNA. 752 35

We have studied cleavage site selection by M1 RNA, the catalytic subunit of Escherichia coli RNase P, under various reaction conditions using tRNA precursors which are cleaved at two positions. Our results showed that the preference of cleavage site changed with variations in pH or Mg2+ concentration. By contrast, no difference in cleavage site selection was observed with increasing pH in the presence of Ca2+ as the only divalent metal ion. Depending on the identity of the nucleotide at position "+ 72", replacement of Mg2+ with Ca2+ resulted in a change of the main cleavage site irrespective of pH. We conclude that cleavage in the presence of Ca2+ compared to cleavage in the presence of Mg2+ has different structural requirements at and near the cleavage site. UV cross-linking revealed that close points between M1 RNA and its substrate were the same irrespective of pH or the identity of the divalent cation. Our results also showed that the observed pH effects are due to changes in the catalytic cleavage rates rather than to global, structural rearrangements. These data are discussed in terms of metal ion binding near the cleavage sites in the enzyme-substrate complex.
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PMID:Cleavage site selection by M1 RNA the catalytic subunit of Escherichia coli RNase P, is influenced by pH. 752 66

We synthesized a chimeric RNA between the catalytic RNA subunit of RNase P from Escherichia coli (M1 RNA) and a model substrate of the enzyme. The model substrate is the smallest substrate of RNase P, having a simple stem-loop structure. This model substrate was added to the 3'-end of M1 RNA. This chimeric molecule, which we call M1 RNA-MS, is a self-cleaving RNA and is cleaved much more efficiently than the M1 RNA-pre-tRNA, an artificial self-cleaving RNA previously synthesized [Kikuchi et al. (1993) Nucleic Acids Res. 21, 4685-4689], that consists of a full-size tRNA precursor and the M1 RNA. The self-cleavage of M1 RNA-MS at 10 mM Mg2+ was an intramolecular reaction (cis-cleavage). Ca2+ supported the self-cleavage of M1 RNA-MS as effectively as Mg2+, although the self-cleavage of M1 RNA-pre-tRNA proceeded with low efficiency in the presence of Ca2+ as the only metal ion. Future application of the M1 RNA-MS molecule to the in vitro evolution of the M1 RNA and other experiments is proposed.
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PMID:Synthesis and self-cleavage reaction of a chimeric molecule between RNase P-RNA and its model substrate. 753 87

The pathway is described for activation by Mg2+ of substrates for M1 RNA, the catalytic subunit of the RNase P from Escherichia coli. The dissociation constants are reported for binding of Mg2+ to the substrate and for the binding of the metal ion-substrate complex to the enzyme. The enzyme binds the substrate with the same affinity whether or not Mg2+ is already bound to the substate. However, only substrates with bound Mg2+ can make a productive ternary complex when combined with the enzyme. The presence of certain 2'-hydroxyl groups in the substrate is required to stabilize the binding of Mg2+ and, thereby, to increase the lifetime of the ternary complex. An energy profile for the reaction of M1 RNA with a small model substrate is presented and the role of Mg2+ bound to the substrate is discussed.
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PMID:Pathway of activation by magnesium ions of substrates for the catalytic subunit of RNase P from Escherichia coli. 768 57


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