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

---

Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nucleoside triphosphate phosphohydrolase [EC 3.6.1.15] activity was found to be included in silkworm cytoplasmic polyhedrosis (CP) virus, which synthesizes mRNA carrying the 5'-terminal modification. This enzyme releases orthophosphate from the gamma-position in a nucleoside triphosphate, leaving nucleoside diphosphate. The rate of hydrolysis of ATP is faster than that of any other ribonucleoside triphosphate. Deoxy ATP is hydrolyzed rather faster than ATP. However, polynucleotides carrying triphosphate at the 5'-terminus, that is, 4S RNA which was synthesized by E. coli RNA polymerase [EC 2.7.7.6] using calf thymus DNA as a template, and the phage Q beta RNA (30S), are not effective substrates for this enzyme. Although the CP virion loses the viral genome and one kind of protein component on proteolytic treatment with pronase, the partially degraded virion still retains phosphohydrolase activity. The phosphohydrolase must therefore be associated firmly with the virion. This enzyme does not require the presence of nucleic acid for its function. Phosphohydrolysis of ATP by this enzyme activity represents a first step in the synthesis of the 5'-terminal modified mRNA of CP virus.
...
PMID:Nucleoside triphosphate phosphohydrolase associated with cytoplasmic polyhedrosis virus. 1 44

Nucleoside triphosphate phosphohydrolase (NTPase) activity was found in a preparation of E. Coli RNA polymerase. This enzymatic activity is capable of hydrolysing all four ribonucleoside triphosphates to the nucleoside diphosphates. However, during in vitro RNA synthesis directed by poly(dC) or poly(dT), only the non-complementary nucleoside triphosphate of the same heterocyclic class was hydrolysed. No incorporation of the non-complementary precursor into RNA could be detected in these experiments. When another RNA polymerase preparation, devoid of NTPase activity, was employed, there was no hydrolysis of any nucleoside triphosphate and significant incorporation of non-complemtary precursor into RNA was observed. These observations lead us to the conclusion that NTPase, acting in conjunction with RNA polymerase, has the function of correcting errors in transcription.
...
PMID:A possible mechanism responsible for the correction of transcription errors. 22 87

Standard preparations of Escherichia coli RNA polymerase (RNAP) contain NTPase activity. High-performance anion-exchange chromatography on Mono Q has recently been used by Hager et al. [1990, Biochemistry 29, 7890-7894] to fractionate RNAP into holoenzyme (alpha 2 beta beta' sigma) and core (alpha 2 beta beta') forms, plus other protein components. We found that one of these components, of protomer size slightly larger than the sigma 70 subunit, has NTPase activity; it is efficiently separated on Mono Q, leaving transcriptionally active holoenzyme and core apparently free of NTPase activity. Because of the similarity in size with sigma 70, the NTPase component may escape detection by routine gel electrophoresis.
...
PMID:Identification of a component separated on Mono Q purification of Escherichia coli RNA polymerase as an NTPase. 131 87

A novel transcriptional proofreading mechanism associated with the beta-subunit of wild-type RNA polymerase from Escherichia coli is suggested from the following data. The purified holoenzyme contains an NTPase activity which specifically converts noncognate NTPs to their corresponding NDP in a template-dependent manner during in vitro transcription of synthetic single- and double-stranded templates. In contrast, purified enzyme from an rpoB mutant which shows increased transcriptional error lacked template-dependent NTP hydrolytic activity. The NTP hydrolytic activity of wild-type enzyme was critically dependent on the integrity of the initiation complex, and required continued transcriptional elongation. Transcription and translation of the lacZ gene proceeded 17% faster in the mutant than in its wild-type parent. These results are discussed in terms of a proofreading model in which the rate of transcription is limited by proofreading events that involve recognition and hydrolysis of noncognate NTPs before they can be misincorporated into RNA.
...
PMID:Transcriptional proofreading in Escherichia coli. 255 56

The effects of pyrophosphate on RNA binding and ATPase activities of Escherichia coli transcription termination factor rho have been studied. Mutant rho-115 protein has a temperature-sensitive RNA-dependent ATPase activity due to the thermolability of binding to RNA [Kent, R.B. & Guterman, S.K. (1981) Fed. Proc. Fed. Am. Soc. Exp. Biol. 40, 1765 (abstr.)]. The presence of either ATP or pyrophosphate at comparable concentrations stabilizes the binary complex of rho and poly(C) at high temperature. ADP at 8-fold greater concentration also stabilizes the mutant rho-RNA binary complex. Pyrophosphate is a noncompetitive inhibitor (Ki = 0.07 mM) of rho poly(C)-dependent ATPase, an activity that is required for rho-mediated termination. These results suggest the existence of a regulatory site on the rho molecule. We suggest that rho NTPase is regulated by RNA polymerase (EC 2.7.7.6) so that during transcription elongation the RNA polymerase competes successfully with rho for substrates and inhibits rho NTPase with product pyrophosphate. Further, RNA polymerase pausing may result in reduced pyrophosphate and increased NTP concentrations, allowing rho NTPase to function.
...
PMID:Pyrophosphate inhibition of rho ATPase: a mechanism of coupling to RNA polymerase activity. 612 40

Poliovirus infection leads to the appearance of a number of cytoplasmic vacuoles involved in the replication of virus genomes. To characterize the viral proteins involved in membrane proliferation different poliovirus proteins have been expressed in HeLa cells. Two recombinant vaccinia viruses have been obtained that express poliovirus protein 2C, one under the 5' untranslated (UTR) sequence of poliovirus and another under the leader region of EMC virus. Expression of 2C was very efficient in both cases, although better results were obtained when poliovirus 2C was expressed under the 5'UTR sequence of EMC virus. Transient expression of poliovirus proteins 2B, 2C or 2BC placed under a T7 promoter was analyzed using a recombinant vaccinia virus that contains the bacteriophage T7 RNA polymerase. The expression of 2C, or 2BC, contrary to 2B, was able to induce the proliferation of vacuoles morphologically similar to those found during poliovirus infection. These findings indicate that poliovirus protein 2C, in addition to its NTPase and RNA binding activities, is also endowed with the capacity to induce the formation of cytoplasmic vacuoles.
...
PMID:Induction of membrane proliferation by poliovirus proteins 2C and 2BC. 781 52

The double-stranded RNA bacteriophage phi 6 contains a virion-associated RNA-dependent RNA polymerase complex. Removal of the virus envelope and the nucleocapsid surface protein, P8, reveals a nucleocapsid core particle (proteins P1, P2, P4, P7) which is the viral polymerase complex, capable of synthesizing RNA strands of positive polarity. The in vitro plus strand synthesis (transcription) reaction of the particle obtained from the mature virion was optimized and its activation and inactivation were investigated. Purine nucleoside triphosphates (NTPs), binding to a low-affinity binding site in the polymerase complex, activated plus strand synthesis. GTP was the preferred NTP, but dGTP, ddGTP, and the noncleavable analog GMP-PCP could also switch on transcription. This NTP-binding site is probably different from that of the unspecific viral NTPase found in protein P4 and also from that of the rNTP-specific RNA polymerase active site. Binding of purine NTPs was sufficient for the switch-on; hydrolysis of the NTP was not required. Besides nucleotides, divalent cations had an effect on phi 6 in vitro plus strand synthesis. Magnesium ions are required for the activity but calcium ions inhibit the reaction. Manganese ions are shown to dissipate the effect of magnesium and calcium ions, leading to uncontrolled, exceptionally high level plus strand synthesis.
...
PMID:In vitro transcription of the double-stranded RNA bacteriophage phi 6 is influenced by purine NTPs and calcium. 788 44

The NIFA protein of Klebsiella pneumoniae is required for transcription of all nif (nitrogen fixation) operons except the regulatory nifLA operon itself. NIFA activates transcription of nif operons by the alternative holoenzyme form of RNA polymerase, sigma 54-holoenzyme, in a nucleoside triphosphate (NTP)-dependent manner. NIFL antagonizes the action of NIFA in the presence of molecular oxygen or combined nitrogen. The NIFA protein of K. pneumoniae is composed of three domains: an N-terminal domain with unclear function, a central catalytic domain, and a C-terminal DNA-binding domain. We report that the isolated central domain of NIFA activates transcription in vitro and that this activation requires NTP with a hydrolyzable beta-gamma bond, as does activation by intact NIFA. Transcriptional activation by the isolated central domain has the heat lability characteristic of intact NIFA and is inhibited by NIFL. The central domain has an NTPase activity that is also heat-labile but is not inhibited by NIFL. Taken together, these results imply that NIFL interferes with contact between NIFA and sigma 54-holoenzyme.
...
PMID:The isolated catalytic domain of NIFA, a bacterial enhancer-binding protein, activates transcription in vitro: activation is inhibited by NIFL. 827 50

A transcription termination factor (Rho) was purified from the Gram-positive bacterium Micrococcus luteus, and the complete gene sequence was determined. The M. luteus Rho polypeptide has 690 residues, which is 271 residues more than its homolog from Escherichia coli. Most of the additional residues compose a highly charged, hydrophilic segment that is inserted in a non-conserved region between two conserved regions of the RNA-binding domain of the known Rho homolog proteins. This segment extends from residues 49 to 311 and includes a stretch of 238 residues that contain no hydrophobic side chains. Biochemical studies indicate that the M. luteus protein is very similar to E. coli Rho in terms of its RNA-dependent NTPase activity and its sensitivity to the Rho-specific inhibitor bicyclomycin. However, the M. luteus protein has a less stringent RNA cofactor specificity. It also acts to terminate RNA transcription with E. coli RNA polymerase on the lambda cro DNA template, but at much earlier termination stop points than those recognized by E. coli Rho. Thus, the M. luteus protein functions as a true Rho factor, but with a different specificity than that of E. coli Rho. We propose that this altered specificity is consistent with its need to function on transcripts that have a high content of G + C residues.
...
PMID:Characterization of an unusual Rho factor from the high G + C gram-positive bacterium Micrococcus luteus. 855 81

Standard preparations of Escherichia coli RNA polymerase harbor a 70 kDa protein with NTPase (beta-gamma cleavage) activity that is not a recognized polymerase subunit. The NTPase activity of this component, before and after separation from the polymerase, is strongly dependent on the presence of DNA; single-stranded polydeoxynucleotides are more effective than double-stranded. ATP and GTP are cleaved, the latter much less readily. The NTPase as it occurs with the polymerase displays cleavage preference for NTPs that are not complementary to the DNA, a fact that has led to proposals for involvement of the NTPase in transcriptional error prevention [Volloch, V. Z., Rits, L. & Tumerman, L. (1979) Nucleic Acids Res. 6, 1535-1546; Libby, R. T., Nelson, J. L., Calvo, J. M., & Gallant, J. A. (1989) EMBO J. 8, 3253-3158]. We find, however, that the lesser cleavage in the presence of complementary DNA results from competition for the NTP between the processes of incorporation by the polymerase and of cleavage by the NTPase, operating on the same substrate pool. The greater cleavage with noncomplementary DNA occurs because of the lack of incorporation by the polymerase, which then does not compete with the NTPase for the substrate pool. Thus, these findings indicate that the cleavage preference of the NTPase for noncomplementary NTPs is not part of a mechanism for error prevention during transcription.
...
PMID:Specificity of an Escherichia coli RNA polymerase-associated NTPase. 939


1 2 3 Next >>

---