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Query: EC:2.7.7.8 (polynucleotide phosphorylase)
 723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly (2'-chloro-2'-deoxyadenylic acid) and poly (2'-bromo-2'-deoxyadenylic acid) were synthesized from the corresponding diphosphates with the aid of polynucleotide phosphorylase from E. coli. UV, CD, acid titration and mixing with poly (U) were investigated. Comparing these properties with those of poly (A) and poly (2'-azido-2'-deoxyadenylic acid), it was found that 2''substituents exert significant effects on the thermal stability of these polynucleotides, though the overall conformational structure was not greatly changed.
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PMID:Polynucleotides. L. Synthesis and properties of poly (2'-chloro-2'-deoxyadenylic acid) and poly (2'-bromo-2'-deoxyadenylic acid). 34 Oct 84

Native Escherichia coli polynucleotide phosphorylase can be retained on blue-dextran--Sepharose. The bound enzyme cannot be displaced by its mononucleotide substrates such as ADP, UDP, CDP, GDP and IDP, but it is easily eluted by its polymeric substrates. Under identical conditions, lactate dehydrogenase, bound on blue-dextran--Sepharose, is not eluted by poly(I) but can be specifically displaced by NADH. On the other hand, the trypsinized polynucleotide phosphorylase, known to be an active enzyme which has lost its polynucleotide site, does not bind to the affinity column. The native polynucleotide phosphorylase can also be tightly bound to poly(U)--agarose and displaced from it only by high salt concentration. The trypsinized enzyme is not bound at all on poly(I)--AGAROSe. Moreover, the native enzyme linked on blue-dextran--Sepharose, remains active indicating a free access of nucleoside diphosphates to the active center. These results taken together show that the dye ligand is not inserted onto the mononucleotide binding site and suggest rather that it binds to the polynucleotide binding region. The implications of this study and the application of blue-dextran--Sepharose affinity chromatography to other proteins having affinity for nucleic acids are discussed.
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PMID:Blue-dextran--Sepharose affinity chromatography: recognition of a polynucleotide binding site of a protein. 34 36

Localization, physico-chemical and catalytic properties and possible biological functions of polynucleotide phosphorylase (PNPase) from animal tissues are discussed. In animal tissue cells PNPase has multiple localization; the major amount of the enzyme is localized in the endoplasmic reticulum ribosomes. In the nuclei PNPase, similar to other endo- and exo-RNAses participates in the processing of precursor molecules of mature forms of RNA, whereas in the cytoplasm it is involved in the destruction of polyribosomes in the polyribosomes of rapidly growing tissues the activity of PNPase is extremely decreased. The mechanisms regulating the PNPase activity in rapidly growing tissues are discussed.
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PMID:[Animal tissue polynucleotide phosphorylase]. 35 Feb 93

Analytical high-pressure anion-exchange chromatography on RPC-5 has been used to study the behaviour of a good primer, d(pT-T-A-G), and a poor primer, d(pT-T-T-T-T-T) in the E. coli polynucleotide phosphorylase-catalysed reactions of dADP, dCDP, dGDP and dTDP where the primer is extended, predominantly, by one or two nucleotides. The experiments provide some generalizations for obtaining optimal yields in preparative reactions. In the course of the experiments, examples of anomalous behaviour of oligonucleotides on RPC-5 were encountered and these are discussed.
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PMID:Enzymatic synthesis of oligodeoxyribonucleotides of defined sequence. Polynucleotide phosphorylase catalysed addition of deoxyribonucleotides to primers which are good or poor acceptors. 35 63

The E. coli polynucleotide phosphorylase-catalysed reaction of the deoxynucleoside 5'-diphosphates of 5-methyldeoxycytidine, N4-hydroxydeoxycytidine, deoxyuridine and 5-mercurideoxyuridine with the primers d(pT-T-A-G) and d(pT-T-T-T-T-T) have been studied under conditions where the primer is extended, predominantly, by one or two nucleotide residues. In experiments with 5-mercurideoxyuridine 5'-diphosphate, no 5-mercurideoxy-uridine-containing oligonucleotides were produced. The other three nucleotide analogs were found to be good substrates for E. coli PNPase and the conditions established for synthesis with these analogs will allow the construction of a number of biologically useful types of oligodeoxyribonucleotide.
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PMID:Enzymatic synthesis of oligodeoxyribonucleotides of defined sequence. Polynucleotide phosphorylase catalysed synthesis using pyrimidine analog-containing deoxyribonucleoside 5'-diphosphates. 35 64

Poly(A) synthesis and degradation have been examined in Escherichia coli cells made permeable to nucleotides by treatment with toluene. Although newly synthesized poly(A) is normally rapidly degraded in this system, extraction of the soluble portion of the cell effectively eliminates this process without affecting poly(A) synthesis. Poly(A) synthesis in this system displays many properties associated with poly(A) synthesis by purified poly(A) polymerase in vitro including a lag in polymerization, stimulation by increased ionic strength, and a low Mg2+ optimum. As with the purified enzyme, this system uses both ADP and ATP as substrates, requires conversion of ATP to ADP, and is strongly inhibited by dADP, orthophosphate, and pyrophosphate. In contrast to the purified poly(A) polymerase, the permeable cell system displays some properties suggestive of in vivo poly(A) metabolism. Thus, the permeable cells require an endogenous RNA primer for activity, the poly(A) product remains with the cells, and the reaction is greatly stimulated by polyamines. This system should prove extremely useful for studies of poly(A) metabolism in E. coli. A surprising feature of these studies was the finding that mutant strains deficient in polynucleotide phosphorylase were unable to synthesize poly(A). The possible roles of polynucleotide phosphorylase and poly(A) in E. coli are discussed.
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PMID:Synthesis and degradation of poly(A) in permeable cells of Escherichia coli. 35 56

Chemically synthesized 2-azaadenosine 5'-diphosphate (n2ADP) and 2-azainosine 5'-diphosphate (n2IDP) were polymerized to yield poly(2-azaadenylic acid), poly(n2A), and poly(2-azainosinic acid), poly(n2I), using Escherichia coli polynucleotide phosphorylase. In neutral solution, poly(n2A) and poly(n2I) had hypochromicities of 32 and 5.5%, respectively. Poly(n2A) formed an ordered structure, which had a melting temperature (Rm) of 20 degrees C at 0.15 M salt concentration. Upon mixing with poly(U), poly(n2A) formed a 1 : 2 complex with Tm of 41 degrees C at 0.15 M salt concentration. Poly(n2A) and poly(n2I) formed three-stranded complexes with poly(I), and poly(A), respectively. Poly(n2A) . 2poly(I), poly(A) . 2poly(n2I), and poly(n2A) . 2poly(n2I) complexes had Tm values of 23, 48, and 31 degrees C at 0.15 M salt concentration, respectively. Poly(n2I) formed a double-stranded complex with poly(C), but its Tm was very low.
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PMID:Polynucleotides. XLIV. Synthesis and properties of poly (2-azaadenylic acid) and poly(2-azainosinic acid). 36 Oct 91

The synthesis of poly(mo5U) requires a high concentration (2.7 mg/ml) of polynucleotide phosphorylase as well as a long reaction time (48 h). The resulting polynucleotide has a chain length of approximately 100 nucleotides. It shows no indication of a stable secondary structure. When poly(mo5U) is mixed with poly(A), a triple-stranded complex poly(A) . 2poly(mo5U) is formed. This complex has a melting temperature of 68.5 +/- 0.5 degrees C at 150 mMNa+ and exhibits a hysteresis loop between melting and reformation of the complex having a delta Tm of 11.5 degrees C. Poly-5-methoxyuridylic acid stimulates the binding of Phe-tRNA to 70-S ribosomes but is inactive in directing poly(Phe) synthesis.
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PMID:Physical and coding properties of poly(5-methoxyuridylic) acid. 37 83

E. coli tryptophanyl-tRNA synthetase can form a complex with Blue-dextran Sepharose, in the presence or in the absence of Mg++. In its absence, the complex is dissociated by either ATP or cognate tRNATrp. However, in the presence of Mg++, only tRNATrp can dissociate the complex whereas ATP has no effect. E. coli total tRNA or tRNAMet, at the same concentration, cannot displace the synthetase from the complex. It is suggested that the Blue-dextran binds to the synthetase through its tRNA binding domain. This hypothesis is supported by previous findings with polynucleotide phosphorylase showing that Blue-dextran Sepharose can be used in affinity chromatography to recognize a polynucleotide binding site of the protein. The selective elution by its cognate tRNA of Trp-tRNA synthetase bound to Blue-dextran Sepharose provides a rapid and efficient purification of the enzyme. Examples of other synthetases and nucleotidyl transferases are also discussed.
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PMID:Blue dextran Sepharose chromatography of the tryptophanyl-tRNA synthetase of E. coli: a potential application for the purification of the enzyme. 37 31

The interaction of pyridoxal, pyridoxal-5'-mono-, di- and triphosphate with certain enzymes of polynucleotide synthesis (DNA-dependent RNA polymerase, DNA-dependent DNA polymerase I and polynucleotide phosphorylase from Escherichia coli and terminal deoxyribonucleotide transferase from calf thymus) was studied. All compounds tested was found to be reversible and competitive inhibitors of these enzymes. The reduction of the enzyme-inhibitor complex with NaBH4 gives rise to the complete irreversible inhibition of the enzymes under study. The comparison of the inhibition constants for pyridoxal and its phosphorylated derivatives with those for mono-, di- and triphosphates of nucleosides was carried out for the enzymes. The results obtained suggest that the modified epsilon-amino-group of lysine residue should be localized at the catalytic site in the vicinity of the pyrophosphate binding area of an enzyme.
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PMID:[Interaction of oligophosphates of pyridoxal with certain enzymes of polynucleotide synthesis]. 38 98


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