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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The polyelectrolyte theory can provide an interpretation of the interdependence of pH, ionic strength, and polyamines one observes in the activity of ribonuclease acting on RNA. According to this theory: (i) A nucleic acid-enzyme complex and the suspending medium may be considered as two phases in equilibrium, even though within limits, the complex is soluble in water. (ii) The enzymatic catalysis is under tight control of the electrostatic potential generated by the system. Consequently, modification in electrostatic potential will induce a concomitant change in activity. (iii) The electrostatic potential can be modified through action on the system of "modulators", either "external" (ionic strength, pH, temperature, etc.) or "internal" (specific ligands, substrates, protein factors, etc.). Similarities between the reaction of ribonuclease (ribonuclease 3'-pyrimidino-oligonucleotidohydrolase; EC 3.1.4.22) and RNA and those observed with highly organized systems catalyzing DNA, RNA, and protein synthesis suggest that the electrostatic potential also provides an important regulatory mechanism in genetic translation. In this view, an essential function of nucleic acids is to provide their enzyme partners with polyanionic microenvironments within which their catalytic activities are controlled by variation in physicochemical parameters, including the proton concentration induced through "modulation" of the local electrostatic potential.
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PMID:Ionic regulation in genetic translation systems. 1 51

The properties of the enzyme ribonuclease N were investigated. By comparing the distribution in the cell of RNase N with the bonafide intracellular beta-galactosidase, and the periplasmic alkaline phosphatase enzymes, we showed that RNase N is an intracellular enzyme. Since previous studies suggested that it is an endoribonuclease, it was compared to RNase III, the only other known intracellular endoribonuclease in Escherichia coli. Using homopolymers and co-polymers we found that, while RNase III could digest double-stranded RNA only, RNase N digested single-stranded and double-stranded RNA with similar efficiency. Furthermore, all RNAs used, natural as well as synthetic, were substrates for the enzyme. Using 5 S rRNA as a substrate it was confirmed that the enzyme is an endonuclease. The final products of the reaction of this enzyme are 5'-mononucleotides. The molecular weight of the enzyme is about 120,000 and it seems to contain two subunits which are similar in size. These properties thus differentiate this enzyme from all other known ribonucleases in E. coli.
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PMID:Characterization of an endoribonuclease, RNase N, from Escherichia coli. 9

The metabolism of mRNA from the lactose (lac) operon of Escherichia coli has been studied in ribonuclease (RNase) III-deficient strains (rnc-105). The induction lag for beta-galactosidase from the first gene was twice as long, and enzyme synthesis was reduced 10-fold in one such mutant compared with its isogenic rnc+ sister; in the original mutant strain AB301-105, synthesis of beta-galactosidase was not even detectable, although transduction analysis revealed the presence of a normal lac operon. This defect does not reflect a loss of all lac operon activity galactoside acetyltransferase from the last gene was synthesized even in strain AB301-105 but at a rate several times lower than normal. Hybridization analyses suggested that both the frequency of transcription initiation and the time to transcribe the entire operon are normal in rnc-105 strains. The long induction lag was caused by a longer translation time. This defect led to translational polarity with reduced amounts of distal mRNA to give a population of smaller-sized lac mRNA molecules. All these pleiotropic effects seem to result from RNase III deficiency, since it was possible to select revertants to rnc+ that grew and expressed the lac operon at normal rates. However, the rnc-105 isogenic strains (but not AB301-105) also changed very easily to give a more normal rate of beta-galactosidase synthesis without regaining RNase III activity or a faster growth rate. The basis for this reversion is not known; it may represent a "phenotypic suppression" rather than result from a stable genetic change. Such suppressor effects could account for earlier reports of a noninvolvement of RNase III in mRNA metabolism in deliberately selected lac+ rnc-105 strains. The ribosomes from rnc-105 strains were as competent as ribosomes from rnc+ strains to form translation initiation complexes in vitro. However, per mass, beta-galactosidase mRNA from AB301-105 was at least three times less competent to form initiation complexes than was A19 beta-galactosidase mRNA. RNase III may be important in the normal cell to prepare lac mRNA for translation initiation. A defect at this step could account for all the observed changes in lac expression. A potential target within a secondary structure at the start of the lac mRNA is considered. Expression of many operons may be affected by RNase III activity; gal and trp operon expressions were also abnormal in RNase III- strains.
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PMID:Altered mRNA metabolism in ribonuclease III-deficient strains of Escherichia coli. 9 20

A new ribonuclease has been isolated from Escherichia coli. The enzyme is present in the 100,000 times g supernatant fraction and has been purified over 200-fold. Studies of the enzyme reveal that: 1. The enzyme shows a marked preference for oligoribonucleotides; indeed, the reaction rate is inversely proportional to the chain length of the substrate. The enzyme does not attack polynucleotides even at high concentrations of enzyme and has no detectable DNase activity. 2. The enzyme is stimulated strongly by Mn2+, less strongly by Mg2+, and not at all by Ca2+ and monovalent cations. 3. The enzyme is purified free of RNase I, RNase II, RNase III, polynucleotide phosphorylase, and other known ribonucleases of E. coli. The enzyme displays identical properties when isolated from mutants of E. coli that are deficient in the above ribonucleases. 4. The enzyme has a marked thermostability, a point of further distinction from RNase II.
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PMID:A novel oligoribonuclease of Escherichia coli. I. Isolation and properties. 24 Aug 24

Serum RNase (RNase I; ribonuclease 3'-pyrimidino-oligonucleotidohydrolase, EC 3.1.4.22) activity (mean +/- SD) with polycytidine as substrate was determined in normal individuals (24.9 +/- 3.0 units/ml) and in patients with pancreatic cancer (37.3 +/- 14.8), pancreatitis (38.5 +/- 12.6), nonpancreatic diseases (48.7 +/- 14.8), or renal failure (175.8 +/- 92.8). Patients with pancreatic cancer could not be distinguished from those with pancreatitis or with nonpancreatic disease, although the RNase activities in all of these differed from the activity in normal individuals. The serum RNase activities of four patients with resectable "curable") pancreatic carcinoma and two others with advanced pancreatic cancer without obstructive jaundice were normal. After total pancreatectomy, serum RNase activity remained in the high-normal range. The data presented here and data in the literature show that serum RNase cannot be of primarily pancreatic origin. The present study also demonstrates that measurement of its activity is not useful in early detection of pancreatic cancer.
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PMID:Serum RNase in the diagnosis of pancreatic carcinoma. 28 51

A comparison of isogenic RNase III+ and RNase III- strains of Escherichia coli shows that although both synthesize precursor and mature 16 S and 23 S ribosomal RNAs, the transient rRNA species of the RNase III- strain differ from those of the RNase III+ strain. The RNase III+ strain synthesizes p16 and p23 rRNA, whereas the RNase III- strain produces unstable 17 S, 18 S, "p23," 25 S and 30 S RNA molecules. The 30 S RNA, which is a primary transcript of the ribosomal RNA gene cluster, does not contribute significantly to any of the smaller RNAs, nor is m23 rRNA derived from 25 S but rather from "p23" RNA. Mature 16 S rRNA is derived from both 18 S and 17 S RNA, and 17 S RNA can be derived from 18 S. Additionally, an unstable RNA species about 300 bases long is missing in the RNase III- strain and another species which seems to be about 50 bases larger appears. Processing of the primary ribosomal RNA transcript in RNase III- strains of Escherichia coli is accomplished during its transcription by two independent pathways which are not so utilized in RNase III+ strains. One pathway yields 18 S and precursor 23 S RNAs which are processed to mature rRNAs; the second pathway yields 25 S RNA and perhaps 16 S rRNA. The second pathway, unlike the first, is inhibited by chloramphenicol treatment. At slow rates of ribosomal RNA synthesis, the nascent transcript is processed preferentially by the first pathway. We suggest that in the absence of RNase III, which is involved in the primary processing of rRNA in E. coli, other enzymes involved in primary and secondary processing of rRNA in RNase III+ cells can recognize their sites on the nascent rRNA transcript and accomplish the primary processing.
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PMID:Multiple pathways for primary processing of ribosomal RNA in Escherichia coli. 32 60

Transmission electron microscopy was used to examine active ribosomal ribonucleic acid (rRNA) genes in two strains of Escherichia coli: N2077, deficient in the enzyme responsible for proper cleavage of the 16S sequence from the elongating nascent rRNA transcript; and N2076, functional in ribonuclease (RNase) III activity, yet otherwise isogenic to N2077. In the strain with wild-type RNase III, double gradients corresponding to a pattern of 16S-cleavage-23S transcription were observed. However, the RNase III-deficient strain exhibited a single ribosomal gradient of approximately the same length as the combined 16S-23S gradients of the wild-type strain. When the rRNA genes were somewhat loosely packed with RNA polymerases, a few of the nascent chains in the ribosomal matrixes of the RNase III-deficient strain were cleaved, but most appeared to be unprocessed. The completed, uncleaved transcripts originating from these gradients are believed to be 30S rRNA molecules recently characterized by biochemical probes.
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PMID:Visualization of ribosomal ribonucleic acid synthesis in a ribonuclease III-Deficient strain of Escherichia coli. 33 50

Mutants of Escherichia coli deficient in ribonuclease III are nonmotile. All transductants and revertants that regained ribonuclease III also regained motility, and all transductants that remained or became rnc are nonmotile, although only some of the revertants that regained motility also became ribonuclease III+.
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PMID:Ribonuclease III is involved in motility of Escherichia coli. 34 82

The size of lysozyme mRNA from T7-infected E. coli RNase III+ and RNase III- strains was analyzed by sucrose gradient sedimentation, dimethylsulfoxide (Me2SO) sucorse gradient sedimentation, and preparative gel electrophoresis. Each technique revealed a similar size distribution of multiple lysozyme mRNA's. Analysis by preparative gel electrophoresis of RNA extracted after infection of Escherichia coli Bst (RNase III+) separated lysozyme mRNA into six peaks of activity ranging in size from 0.2 x 10(6) to 1.9 x 10(6) daltons. Four well-resolved major peaks of activity were detected, having apparent molecular weights of approximately 0.61 x 10(6), 0.76 x 10(6), 0.92 x 10(6), and 1.3 x 10(6). A broad band of activity, with a molecular weight range from 0.2 x 10(6) to 0.37 x 10(6), was also present, and a sixth peak of activity was sometimes observed that migrates with a mobility corresponding to a molecular weight of 1.9 x 10(6). Judging from their molecular weight as estimated by electrophoresis, most, if not all, of the lysozyme mRNA's were polycistronic. The RNA extracted after infection of an RNase III- host contained a more heterogeneous collection of lysozyme mRNA's. In addition to lysozyme mRNA activity on RNAs with molecular weights between 0.2 x 10(6) and 1.9 x 10(6), RNA species with molecular weights estimated at 4 x 10(6) to 5 x 10(6) were also detected. The data indicate that RNase III processes at least some of the primary lysozyme transcripts. The multiple lysozyme mRNA's represent discrete RNA species rather than aggregates because analysis of the size of lysozyme mRNA under completely denaturing conditions, in Me2SO, produced a similar size distribution of lysozyme mRNAs. Also, treatment of RNA with 90% Me2SO, which separates the strands of a completely double-stranded RNA, did not significantly alter the electrophoretic mobility of the lysozyme mRNA.
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PMID:Effect of RNase III on the size of bacteriophage T7 lysozyme mRNA. 35 3

RNase III had no positive effect on the translation of bacteriophage T7 lysozyme mRNA in vivo or in vitro. The time of appearance and quanity of lysozyme in T7-infected E. coli BL107, an RNase III- strain, and T7-infected E. coli BL15, a nearly isogenic RNase III+ strain, were indistinguishable. Nearly identical patterns of lysozyme mRNA activity were obtained when RNA extracted at different times after infection of RNase III+ and RNase III- hosts was translated in cell-free extracts of E. coli containing or lacking RNase III. Exposure of RNA extracted from T7-infected E. coli BL107 (RNase III-) to purified RNase III did not increase the lysozyme mRNA activity of this RNA. The only result that implied that RNase III has a differential effect on the translatability of the lysozyme mRNA was the translation of fractionaed RNA from T7-infected E. coli BL107. Translation of the smallest and largest lysozyme messages, 0.33 x 10(6) and 4 x 10(6) to 5 x 10(6) daltons, was the most inefficient in RNase III- cell-free extracts as compared to RNase III+ cell-free translation. The translation of the most abundant, medium-sized lysozyme mRNA between 0.9 x 10(6) and 1.5 x 10(6) daltons was the least affected by the absence of RNase III. The existence of a lag between the appearance of lysozyme mRNA and the appearance of lysozyme in T7 infection was confirmed. In these studies a very rapid method of RNA extraction was used, eliminating the possibility of continued RNA transcription during cell collection and RNA extraction. With this method of analysis, the length of the lag period was established at about 3 min. The possibility that RNase III is the controlling element of the lag period was eliminated by these investigations.
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PMID:Effect of RNase III on efficiency of translation of bacteriophage T7 lysozyme mRNA. 35 4


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