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

The association of an RNA-dependent RNA polymerase activity with virions of pike fry rhabdovirus has been demonstrated by both in vitro and in vivo studies. The temperature optimum for the in vitro assay is around 20 C, although enzyme activity can be observed at 4 C. Preparations of pike fry virus possess a glycoprotein, a membrane protein, a nucleoprotein, an L protein, and a phosphoprotein, as well as an RNA of about 3.8 times 10-6 mol wt. A protein kinase activity has been found associated with virus preparations. In vitro RNA product analyses indicate that the virus-associated enzyme functions principally as a transcriptase synthesizing viral-complementary, heteropolymeric RNA.
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PMID:RNA polymerase associated with virions of pike fry rhabdovirus. 116 3

The genome of Epstein-Barr virus (EBV) codes for two non-translated small RNA molecules, EBER 1 and 2. We found that both EBERs are expressed in the major EBV-carrying cell types, group I and III Burkitt's lymphoma (BL) cell lines, lymphoblastoid cell lines (LCLs) and in two nude mouse-passaged nasopharyngeal carcinoma (NPC) tumours. The relative amount of EBER 1 and EBER 2 varied in different host cells but did not correlate with the cellular phenotype. The EBER coding and flanking sequences were predominantly hypomethylated at HpaII sites not only in LCLs which usually carry hypomethylated EBV genomes but also in BL and NPC cell lines harbouring EBV episomes that are highly methylated in other regions. Thus, the EBER transcription units, actively transcribed by RNA polymerase III in the major EBV-carrying cell types, represent a methylation-free region in the EBV genome similarly to regulatory sequences of the latent membrane protein gene when the latter is transcribed by RNA polymerase II.
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PMID:RNA polymerase III-transcribed EBER 1 and 2 transcription units are expressed and hypomethylated in the major Epstein-Barr virus-carrying cell types. 132 Dec 9

micF RNA regulates the levels of outer membrane protein F (OmpF) in Escherichia coli in response to temperature increase and other stress conditions by decreasing the levels of ompF mRNA (Andersen et al., 1989). A 93-nucleotide micF RNA was synthesized in vitro directly from polymerase chain reaction generated DNA which was designed to contain a functional T7 RNA polymerase promoter upstream of the micF RNA gene and an appropriate restriction site for transcription termination. A transcript (150 nucleotides) containing the ribosomal binding domain of ompF mRNA messenger was synthesized in vitro from the ompF gene cloned into a T7 expression vector. A stable duplex was formed between micF RNA and the 150-nucleotide 5' transcript of ompF mRNA after incubation at 37 degrees C in a physiological buffer. The melting curve of the duplex formed by micF RNA and 150-nucleotide transcript revealed a Tm of 56 degrees C and a delta Tm that spans about 20 degrees C; both are consistent with the proposed structure for the micF/ompF duplex. In addition, as determined by competition studies and UV cross-linking/label-transfer analyses, an E. coli protein was found to bind specifically to micF RNA. The protein also bound weakly to the 150-nucleotide ompF transcript. The data are the first to demonstrate the complex between micF RNA and the 5' end of ompF mRNA and suggest that in vivo a micF ribonucleoprotein (RNP) particle may participate in the destabilization ompF mRNA during thermoregulation of OmpF porin.
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PMID:micF RNA binds to the 5' end of ompF mRNA and to a protein from Escherichia coli. 170 97

Mutations in the Bacillus subtilis major RNA polymerase sigma factor gene (rpoD/crsA47) and a sensory receiver gene (spoOA/rvtA11) are potent intergenic suppressors of several stage 0 sporulation mutations (spoOB, OE, OF & OK). We show here that these suppressors also rescue temperature-sensitive sporulation phenotypes (Spots) caused by mutations in RNA polymerase, ribosomal protein, and protein synthesis elongation factor EF-G genes. The effects of the crsA and rvtA suppressors on RNA polymerase and ribosomal protein spots mutations are similar to those previously described for mutations in another intergenic suppressor gene rev. We have examined the effects of rvtA and crsA mutations on the expression of sporulation-associated membrane proteins, including flagellin and penicillin binding protein 5* (PBP 5*). Both suppressors restored sporulation and synthesis of PBP 5* in several spoO mutants. However, only rvtA restored flagellin synthesis in spoO suppressed backgrounds. The membrane protein phenotypes resulting from the presence of crsA or rvtA suppressors in spoO strains suggests that these suppressors function via distinct molecular mechanisms. The rvtA and crsA mutations are also able to block the ability of ethanol to induce spoO phenocopies at concentrations of ethanol which prevent sporulation in wild type cells. The effects of ethanol on sporulation-associated membrane protein synthesis in wild type and suppressor containing strains have been examined.
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PMID:Suppression of defective-sporulation phenotypes by mutations in transcription factor genes of Bacillus subtilis. 174 59

A high molecular weight mitochondrial DNA (mtDNA) replication complex, associated with the mitochondrial membrane, was isolated by sucrose gradient centrifugation from purified wheat embryo mitochondria. This complex comprised the mtDNA as well as enzyme activities involved in the replication and transcription of the organelle genome, such as DNA polymerase, RNA polymerase and topoisomerase type I. The isolated complex is active in mtDNA and mtRNA synthesis in vitro. Electron microscopy and lipid analysis confirmed the membrane origin of this complex. Enzyme activities are resistant to physiological ionic strengths, 0.1-0.2 M KC1, while the membrane-mtDNA association is resistant up to 1 M KC1. DNase treatment of the complex released the DNA polymerase activity while protease treatment solubilized mtDNA, suggesting the direct interaction of mtDNA with membrane protein(s). The use of a novel approach to detect mtDNA fragments specifically retained by the mitochondrial membranes after Sal I digestion of the complex suggests that specific mtDNA sequences anchor mtDNA to mitochondrial membranes.
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PMID:Isolation from wheat mitochondria of a membrane-associated high molecular weight complex involved in DNA synthesis. 189 1

The role of the co-transported cation in the coupling mechanism of the melibiose permease of Escherichia coli has been investigated by analysing its sugar-binding activity, facilitated diffusion reactions and energy-dependent transport reactions catalysed by the carrier functioning either as an H+, Na+ or Li(+)-sugar symporter. The results suggest that the coupling cation not only acts as an activator for sugar-binding on the carrier but also regulates the rate of dissociation of the co-substrates in the cytoplasm by controlling the stability of the ternary complex cation-sugar-carrier facing the cell interior. Furthermore, there is some evidence that the membrane potential enhances the rate of symport activity by increasing the rate of dissociation of the co-substrates from the carrier in the cellular compartment. Identification of the melibiose permease as a membrane protein of 39 kDa by using a T7 RNA polymerase/promoter expression system is described. Site-directed mutagenesis has been used to replace individual carrier histidine residues by arginine to probe the functional contribution of each of the seven histidine residues to the symport mechanism. Only substitution of arginine for His94 greatly interferes with the carrier function. It is finally shown that mutations affecting the glutamate residue in position 361 inactivate translocation of the co-substrates but not their recognition by the permease.
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PMID:The melibiose/Na+ symporter of Escherichia coli: kinetic and molecular properties. 197 Jun 46

The fadL gene of Escherichia coli encodes an outer membrane protein (FadL) that plays a central role in the uptake of exogenous long-chain fatty acids. The nucleotide sequence of the fadL gene revealed a single open reading frame of 1,344 bp encoding a protein with 448 amino acid residues and a molecular weight of 48,831. The transcriptional start, analyzed by primer extension, was shown to be 95 bp upstream from the translational start. Apparent -10 and -35 regions were found at -12 and -37 bp upstream from the transcriptional start. Three regions with hyphenated dyad symmetry (two between the transcriptional start and the translational start and one upstream from the -10 and -35 regions) were identified that may play a role in the expression of fadL. The protein product of the fadL gene contained a signal sequence and signal peptidase I cleavage site similar to that defined for other E. coli outer membrane proteins. The N-terminal sequence of mature FadL protein was determined by automated amino acid sequencing of protein purified from the outer membrane of a strain harboring fadL under the control of a T7 RNA polymerase-responsive promoter. This amino acid sequence, Ala-Gly-Phe-Gln-Leu-Asn-Glu-Phe-Ser-Ser, verified the signal peptidase I cleavage site on pre-FadL and confirmed the N-terminal amino acid sequence of FadL predicted from the DNA sequence. Mature FadL contained 421 amino acid residues, giving a molecular weight of 45,969. The amino acid composition of FadL deduced from the DNA sequence suggested that this protein contained an abundance of hydrophobic amino acid residues and lacked cysteinyl residues. The hydrophobic amino acids within FadL were predicted to contribute to at least five regions of the protein with an overall hydrophobic character. The amino acid sequence of FadL was used to search GenBank for other proteins with amino acid sequence homology. These data demonstrated that FadL and the heat-modifiable outer membrane protein P1 of Haemophilus influenzae type b were 60.5% conserved and 42.0% identical over 438 amino acid residues.
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PMID:Primary sequence of the Escherichia coli fadL gene encoding an outer membrane protein required for long-chain fatty acid transport. 198 39

Nuclear run-on assays revealed extensive transcription of the Epstein-Barr virus genome during latent infection in in vitro-infected human fetal lymphoblastoid cells (IB-4). The EBER genes were the most heavily transcribed viral genes in these cells. Their transcription was partially inhibited in the presence of 1 microgram of alpha-amanitin per ml and fully inhibited at 100 micrograms/ml, consistent with RNA polymerase III transcription. All other transcription was inhibited at 1 microgram of alpha-amanitin per ml, consistent with RNA polymerase II sensitivity to alpha-amanitin. Other than EBER transcription, almost no transcription occurred from the U1 region. Specifically, no transcription was detected from the U1 latent promoter. RNA polymerase II transcription was highest in IR1, extending rightward through U2 and IR2 into the U3 domain and gradually decreased, but was measurable throughout the rest of the genome. This is consistent with EBNA gene transcription initiation within IR1. The higher level of transcription of the IR1 and U2 domains, which encode EBNA-LP and EBNA-2, as opposed to the domains which encode EBNA-3A, EBNA-3B, or EBNA-3C or EBNA-1, correlated with a higher level of EBNA-LP/EBNA-2 mRNA. Transcription extended through U4 into U5, even though no known latent-gene mRNAs are expressed from U4 downstream of the EBNA-1 open reading frame. This may result from inefficient termination of EBNA gene transcription. Leftward transcription from the latent membrane protein promoter was lower than EBNA transcription, although the latent membrane protein mRNA was the most abundant of the latent-gene mRNAs, indicating that this mRNA is more efficiently processed or has a longer half-life. Although transcription was detected from the DL strong early promoters and to a lesser extent from other early promoters, early mRNAs were less abundant than EBNA mRNAs or undetectable, suggesting that there may be posttranscriptional as well as transcriptional control over early mRNA expression in these latently infected cells.
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PMID:Transcription of the Epstein-Barr virus genome during latency in growth-transformed lymphocytes. 215 49

By use of techniques described recently for lac permease [Roepe, P.D., & Kaback, H.R. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 6087], the melibiose permease from Escherichia coli, another polytopic integral plasma membrane protein, has been purified in a metastable soluble form after overexpression of the melB gene via the T7 RNA polymerase system. As demonstrated with lac permease, soluble melibiose permease is dissociated from the membrane with 5.0 M urea and appears to remain soluble in phosphate buffer at neutral pH after removal of urea by dialysis, although the protein aggregates in a time- and concentration-dependent fashion. Moreover, soluble melibiose permease behaves as a monomer during purification by size exclusion chromatography in the presence of urea. Circular dichroism of purified soluble melibiose permease reveals that the protein is highly helical in potassium phosphate buffer and that secondary structure is disrupted in 5.0 M urea. Finally, purified melibiose permease can be reconstituted into proteoliposomes, and the preparations catalyze membrane potential driven H+/melibiose or Na+/methyl 1-thio-beta,D-galactopyranoside symport. The results provide further support for the notion that hydrophobic transmembrane proteins may be able to assume a nondenatured conformation in aqueous solution and extend the implication that the approach described may represent a general method for rapid isolation and reconstitution of this class of membrane proteins.
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PMID:Isolation and functional reconstitution of soluble melibiose permease from Escherichia coli. 218 31

The arsenical resistance (ars) operon of the conjugative R-factor R773 encodes an ATP-driven anion extrusion pump, producing bacterial resistance to arsenicals. There are three structural genes, of which the product of the middle gene, arsB, has not previously been identified. From nucleotide sequence data, the ArsB protein is predicted to be a 45577 Dalton hydrophobic protein. A mini-Mu transposition procedure was used to construct an arsB-lacZ gene fusion, producing a hybrid ArsB-beta-galactosidase protein which was localized in the inner membrane. The operon was cloned into a T7 RNA polymerase expression vector. In addition to the previously identified ArsA and ArsC proteins, the cells synthesized an inner membrane protein with an apparent mass of 36 kD identified as the ArsB protein.
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PMID:Identification of the membrane component of the anion pump encoded by the arsenical resistance operon of R-factor R773. 252 97


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