Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the course of kinetic studies on the synthesis of RNA polymerase subunits in Escherichia coli K12, strain Km7 (CP372), certain anomalies were found that seemed to be associated with the system of reversible inhibition of RNA and protein synthesis by rifampicin. To find a possible explanation for these anomalies, effects of rifampicin on RNA chain elongation and on residual synthesis of polymerase subunits were investigated with several strains including Km7. Examination of mRNA synthesis for the tryptophan operon suggested that RNA chain growth as well as RNA chain initiation is inhibited at high drug concentration (500 mug/ml), wheras RNA chain initiation is inhibited specifically at low concentration (20 mug/ml). Analysis of effect of rifampicin concentration on total RNA synthesis gave results that are also consistent with this conclusion. These results emphasize the need for selecting a proper drug concentration whenever rifampicin or other related antibiotic is used as a specific inhibitor of transcription initiation. When rifampicin was added to a culture of these strains absolute rates of synthesis of all subunits of RNA polymerase increased for several minutes and then decreased. The extent of this transient stimulation varied depending on the strain, drug concentration and other conditions, but was most striking for the beta and sigma subunits with strain Km7 at high drug concentration (500 mug/ml). With a rifampicin-sensitive wild-type strain tested, the maximum stimulation was found at about 50 mug/ml of the drug, with a particularly marked effect for sigma subunit. Streptolydigin, on the other hand, inhibited the synthesis of core subunits much faster than the bulk of protein, but inhibited synthesis of sigma subunit only after a lag. Hence a specific effect of rifampicin but not the inactivation of beta subunit per se appears to be involved in transient stimulation of polymerase synthesis observed. Implications of these findings on the control of RNA polymerase synthesis are discussed.
Mol Gen Genet 1976 Jun 15
PMID:Effects of rifampicin on synthesis and functional activity of DNA-dependent RNA polymerase in Escherichia coli. 78 14

The transcription of the "leader" region (Bronson et al., 1973) of the trp operon in Escherichia coli was studied in normal mutants which delete most of the operator-distal region of the operon [a deletion strain (trp OAEG) retaining only about one third of the "leader" region and two deletion strains (trpOAE14 and trpOAE2) retaining the whole "leader" region and an initial portion of the trpE], as well as in a strain with an intact trp operon, but with a temperature-sensitive lesion in ribosomal protein factor EFTs (strain HAK88). In these deletion mutants, mRNA molecules corresponding to the "leader" region were detected as most of the trp-specific mRNA. Less inhibition of transcription, of the promoter-proximal portion of the trp "leader" region than that of more distal genes of the operon, was found in chloramphenicol-treated cells of strain trpOAE14. It was also observed that transcription of the initial one third portion of the "leader" region was not repressed by tryptophan in strains trpOAE6 and trp OAE14. A similar effect of a translation block on transcription of the distal part of the "leader" region was observed with strain HAK88 at the nonpermissive temperature. In sedimentation analysis of polyribosomes containing the trp mRNA molecules from the deletion mutants, trp mRNA from strain trpOAE14 was found in monosomes and small polyribosomes, whereas the majority of the trp mRNA from strain trpOAE6 was found joined to a single ribosome or ribosomal subunit. These results suggest that ribosomes bind in vivo to a site(s) located in the middle of the "leader" mRNA sequence, and that the initial transcription of the trp operon does not require any connection to functional translational machinery, while continuation of RNA synthesis beyond a first ribosome binding site seems indispensably coupled to ribosome function.
Mol Gen Genet 1976 Jul 23
PMID:Initial trp operon sequence in Escherichia coli is transcribed without coupling to translation. 78 18

The basic conditions for use of a new biochemical assay of bacteriophage induction are described. This method is based on the read-through transcription of the tryptophan operon integrated into an "early" transcribed region of the bacteriophage phi80 or gamma genome. Inactivation of repressor molecules was assayed by measuring, in the presence of tryptophan, anthranilate synthetase activity in an Escherichia coli (trpE-) phi80 or gamma lysogen infected with phi80ptrp or gammaptrp, respectively, and treated with mitomycin C or UV irradiation. This method provides a sensitive and easy means to analyze the induction process.
Mol Gen Genet 1976 Oct 18
PMID:The molecular mechanism of virus induction. I. A procedure for the biochemical assay of prophage induction. 79 Jan 52

The intrinsic tryptophan fluorescence of bacteriophage T4-coded gene 32-protein is found to be partially quenched on binding a variety of mono-, oligo-, and polynucleotides. This phenomenon is exploited to partially "map" the nucleic acid binding site of the protein. The intrinsic fluorescence spectrum of the protein peaks at about 347 nm, compared to 359 nm for the fully solvated model fluorophore, N-acetyl-L-tryptophanamide. Nucleotide binding, or collisional quenching by iodide ion, reduces the intensity of the fluorescence, with little or no peak shift. Small ligands, ranging in size from ribose- and deoxyribose-phosphate to tetranucleotides, quench the fluorescence by 2 to 6%; larger ligands quench from 20 to 35% of the intrinsic protein fluorescence. Iodide quenching experiments subjected to Stern-Vollmer analysis suggest that the binding of short nucleotide-containing ligands brings about a conformational change in the protein, fully exposing a tryptophan side chain to the solvent environment. The fluorescence of this tryptophan is fully quenched by the binding of d(Ap)2, but is largely unaffected by the binding of d(ApA) or d(pA)2, indicating both that this (tryptophan) "reporter" residue is located in the nucleic acid binding site and that binding is polar, i.e. polynucleotide chains of only one orientation are complexed. Long oligonucleotides fully quench the fluorescence of this binding site tryptophan. At high salt concentration (2 M NaCl), gene 32-protein forms self-limited dimers (Carroll, R.B., Neet, K.E., and Goldthwait, D.A. (1972) Proc. Natl, Acad. Sci. U.S.A. 69, 2741-2744; (1975) J. Mol. Biol. 91, 275-291). These dimers, in either high salt or in low salt after cross-linking, fail to bind nucleotides, suggesting that dimer formation partially occludes the nucleic acid binding site and thus that these dimers are probably not involved as intermediates in cooperative protein binding to the DNA. On the other hand, dimerization apparently results in a conformational change which fully exposes the "reporter" tryptophan to iodide quenching. These results are used to formulate a model of some of the nucleic acid-protein and protein-protein interactions involved in the cooperative binding of gene 32-protein to single-stranded DNA.
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PMID:DNA "melting" proteins. III. Fluorescence "mapping" of the nucleic acid binding site of bacteriophage T4 gene 32-protein. 79 46

Two types of lambdatrp phages have been used as model systems to investigate ways of optimising the expression of bacterial genes from transducing phage genomes. Excellent yields of trp enzymes were achieved by infecting a trpR- host with Q- or Q-S- derivatives of lambdatrpAM1, which expresses its trp genese exclusively from the trp promoter. The five trp geneproducts constituted more than 50% of the total soluble protein of infected cells under these conditions, and an even higher proportion of the protein synthesized after infection. In a trpR+ host, phage DNA replication was easily able to override tryptophan-mediated repression by titration of the trp promoter were equally productive, while having the advantage of being much simpler to construct and propagate. lambdatrp phages lacking the trp promoter were used to investigate ways of optimising gene expression initiated at the phage promoter, PL. Though very powerful, the latter promoter is more difficult to harness then the trp promoter. Derepression of transcription from PL by the use of cro- mutations is accompanied by poor replication of transducing phage DNA. Attempts to circumvent this difficulty using virulent of cro,cII double mutants have not been successful. Nevertheless, cells infected with a lambdatrp phage expressing its trp genes exclusively from PL made up to 16 per cent of their protein as trp gene-products.
Mol Gen Genet 1976 Nov 24
PMID:The use of specialised transducing phages in the amplification of enzyme production. 79 72

A study was made of the influence of the growth rate of Escherichia coli bacteria on the transcription of the tryptophan (trp) operon, in various trp repressor negative strains. Selective measurement of the levels of RNA transcribed from the regulatory region (reg) of this operon and from the structural genes, respectively, has revealed that the increase of the rate of trpRNA synthesis with bacterial growth rate (Rose and Yanofsky, 1972) is due to a decrease of the frequency of termination of transcription at the transcriptional barrier in the regulatory region of the operon. In a mutant strain of E. coli with a deletion covering the promotor distal part of the regulatory region of the trp operon where the barrier is located, the rate of trpRNA synthesis is not affected by the growth rate. In suA- strains, in which Rho factor activity is reduced the bacterial growth rate does not affect the rate of synthesis of trpRNA. This result suggests that in wild type bacteria Rho factor contributes to the control of the transcription of the trp operon. In bacteria with a mutation rendering Tryptophanyl-tRNA synthetase (TRSase) inactive (trpS- strains) the rate of trpRNA synthesis is affected by the growth rate in the same way as in the isogenic wild type bacteria. This result indicates that TRSase plays no obligatory role in the control of trpRNA synthesis through a mechanism of termination and anti-termination of transcription, at least not in the studied strains, which carried a relA mutation.
Mol Gen Genet 1976 Dec 22
PMID:A transcriptional barrier in the regulatory region of the tryptophan operon of Escherichia coli: its role in the regulation of repressor-independent RNA synthesis. 79 44

The heavy water (D2O) has been shown to induce the conformational transitions in trypsin, chymotrypsin and pepsin. The transfer of proteins from H2O into D2O results a change in their sensitivity to UV-light. An increase in sensitivity to the irradiation at 248 nm and a decrease in sensitivity to the irradiation at 280 nm were observed. The quantum yield of chromophore photolysis (for cystyne and tryptophan) is correspondingly changed. However, although the quantum yield of sensitized reduction of cystine by solvated electrons photochemically ejected from the aromatic acid residues during irradiation at 280 nm increases instead of a rise a drop in the quantum yield of protein inactivation is registered. The data obtained are discussed in terms of importance of solvated shell for conformational stability of proteins. The solvated electrons are suggested to be transfered mainly to nonessential disulfide bridges within trypsin molecule. Rupture of these bonds does not result in trypsin inactivation.
Mol Biol (Mosk)
PMID:[Influence of heavy water (D20) on the conformation and UV-sensitivity of proteins]. 80 85

1. Subcutaneous injection of adrenaline into normal male volunteer subjects caused large increases of plasma non-esterified fatty acids and free tryptophan, but plasma total tryptophan fell considerably. Therefore increases of the percentage of plasma tryptophan in the free state were more marked than absolute increases of free tryptophan. 2. Plasma tyrosine fell slightly and plasma phenylalanine and cortisol were unaffected. 3. It is suggested that catecholamine release could lead to abnormalities of tryptophan disposition in stress and psychiatric illness.
Clin Sci Mol Med 1977 Sep
PMID:Effects of adrenaline injection on human plasma tryptophan and non-esterified fatty acids. 91 45

Certain ocular proteins have been found to be chemically modified by exposure to near-UV light (320-390 nm) in the presence of tryptophan. Colored and fluorescent tryptophan photoproducts bind firmly to proteins, thereby altering their physico-chemical properties. The question of whether such a reaction would inhibit the catalytic action of catalase is herein raised. When solutions of bovine liver catalase were re-incubated up to 24 hr under near-UV with preirradiated tryptophan and dialyzed, most of the ability of the enzyme to decompose H2O2 was lost. Similar results occurred for catalase activities of bovine cornea and lens epithelia. The enzyme protein exhibited altered UV absorption and fluorescence spectra and increased electrophoretic mobility after binding photoproducts, Near-UV light photoproducts of tryptophan are thus capable of deactivating crystalline and tissue catalase.
Mol Cell Biochem 1976 Jun 15
PMID:Inactivation of catalase by near ultraviolet light and tryptophan photoproducts. 94 May 47

The rates of tryptophanyl-tRNA formation catalyzed by beef pancreas tryptophanyl-tRNA synthetase were measured in a concentration range of each substrate (tryptophan, ATP and yeast tRNATrp) and also in the presence of various concentrations of substrate analogues (tryptamine and alpha,beta-methylene analogue of ATP) concentrations. The data obtained were compared with the kinetic equations which described various possible mechanisms of the reaction. The comparison of the mechanisms was based on the calculation of relative probabilities of each hypothesis the efficiency of which was demonstrated earlier. The calculations have shown that two mechanisms according to which the intermediate enzyme-aminoacyl-adenylate complex formation involves the enzyme-aminoacyl-tRNA complex are the most probable ones.
Mol Biol (Mosk)
PMID:[The mechanism of the reaction forming tryptophanyl-tRNA, catalyzed by tryptophan:tRNA-ligase]. 94 May 60


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