Polysome transitions and the regulation of ribonucleic acid synthesis in Escherichia coli

Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis Protein Banding Patterns among Rhizobium leguminosarum biovar phaseoli Strains Isolated from the Mexican Bean Phaseolus coccineus

Several rhizobial strains were isolated from Phaseolus coccineus root nodules and were determined to be Rhizobium leguminosarum biovar phaseoli strains after reinfection of the same host plant. These strains were characterized by cultural procedures (growth on different carbon sources and intrinsic antibiotic resistance) and electrophoretic procedures (sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins). Our results showed that these rhizobia are very similar to each other, especially in their electrophoretic protein banding patterns, suggesting that they might belong to isolated populations.

Expression of arg genes of Escherichia coli during arginine limitation dependent upon stringent control of translation

The transcription and translation of operons for arginine biosynthetic enzymes after arginine removal (arginine down shift) were studied in relA and relA+ strains of Escherichia coli. After arginine down shift, derepression of synthesis of the arginine biosynthetic enzymes ornithine carbamoyltransferase (argF) and argininosuccinate lyase (argH) began at about 15 min in relA+ cells but was delayed in relA cells for more than 2 h. However, both relA+ and relA cells accumulated high levels of argCBH mRNA, as shown by dot blot hybridization, after arginine down shift. After 15 min of arginine limitation, the proportion of ribosome-bound argCBH mRNA was equivalent in both relA+ and relA cells. During the 15 min after the arginine down shift, relA+ cells produced a significant burst of argF and argH enzyme synthesis when arginine was added back to the culture, whereas relA cells did not produce this burst of enzyme synthesis. The relA cells regained the ability to produce a burst of argF and argH enzyme synthesis when alpha-methylglucose-induced glucose starvation was combined with arginine limitation. Significant guanosine 5'-diphosphate 3'-diphosphate accumulated in relA cells under this condition. Our results support the view that during periods of severe amino acid limitation guanosine 5'-diphosphate 3'-diphosphate acts in some way to ensure the translation of argCBH mRNA.

Differential effect of amino acid starvation on polysome decay in Escherichia coli

In a relA+ strain of E. coli starved separately for each of four required amino acids, the intracellular concentration of polysomes decreases as a function of time in all cases: very rapidly in the absence of arginine or leucine, slowly in the absence of threonine or histidine. In a starved isogenic relA strain, the polysome level is either totally stable or else drops slowly. The decrease in the level, when it occurs, does not significantly affect the polysome size distribution. Models for polysome metabolism in amino acid starved cells are discussed.

Recovery of polysome function of T4-infected Escherichia coli after brief treatment with chloramphenicol and rifampin

T4-infected Escherichia coli cells briefly exposed to rifampin, or to rifampin plus chloramphenicol, were capable of protein synthesis for some time after removal of the antibiotics, although ribonucleic acid synthesis was irreversibly inhibited. Partially completed peptides trapped on polysomes by high levels of chloramphenicol were eventually completed after removal of the drug, as demonstrated by subjecting labeled peptides from appropriate polysome regions to polyacrylamide disc gel electrophoresis. Thus, the effect of the drug appears to be reversible on the molecular as well as the cellular level.

Resolution of the nitrate reductase complex from the membrane of Escherichia coli

A procedure has been developed whereby the components of the nitrate reductase complex from the membrane of Escherichia coli can be extracted by means of a nonionic detergent and separated from each other as discrete elements in an active form. It is not yet clear whether these are the dissociated enzymatic elements or whether they are fragments containing other membrane proteins. In any case, they appeared nearly lipid-free and still active.

Temperature-sensitive mutation in regulation of ribonucleic acid synthesis in Escherichia coli

An Escherichia coli mutant dependent on exogenous transfer ribonucleic acid (RNA) for bulk RNA formation at 42 C has been isolated, starting from a parental strain permeable to RNA. In the absence of added transfer RNA at the high temperature, protein synthesis stopped, and the strain formed little if any ribosomal RNA.

R factor elimination during thymine starvation: effects of inhibition of protein synthesis and readdition of thymine

R factor 1818 is shown to be eliminated from a thymineless strain of Escherichia coli J6-2 (R-1818) during thymine starvation. Readdition of thymine to the starved cultures produces a partial recovery in viable count but does not affect the proportion of R(-) cells. The R factor is not cured from exponential- or stationary-phase cultures which are starved of required amino acids as well as thymine, nor from cells which are deprived of thymine in the presence of chloramphenicol. However, in both of these cases, the extent of thymineless death is reduced. It is suggested that protein synthesis is a requirement for R-1818 elimination, and the possible nature of this protein is discussed.

Polysome turnover during amino acid starvation in Escherichia coli

The experiments presented in this paper support earlier evidence that ribosomes are released from polysomes when they encounter a codon for which no charged transfer ribonucleic acid is available. However, it is further shown that these ribosomes then reinitiate and resume translation. The size and the level of polysomes during deprival of an amino acid is a function of the frequency with which that particular amino acid appears in cellular proteins. Polysomes from starved cells are more stable than those from growing cells, and, moreover, polysomes from starved relaxed strains are more stable than those from starved stringent strains.

The control of ribonucleic acid synthesis in bacteria. The synthesis and stability of ribonucleic acid in chloramphenicol-inhibited cultures of Escherichia coli

The rate of polymerization of ribosomal ribonucleic acid chains was estimated for steadily growing cultures of Escherichia coli M.R.E.600, from the kinetics of incorporation of exogenous [5-(3)H]uracil into completed 23S rRNA molecules. The analytical method of Avery & Midgley (1971) was used. Measurements were made at 37 degrees C, in the presence or the absence of chloramphenicol, in each of three media; enriched broth, glucose-salts or sodium lactate-salts. The rate of chain elongation of 23S rRNA was virtually constant in all media at 37 degrees C, as 24+/-4 nucleotides added/s. Accelerations in the rate of biosynthesis of rRNA by chloramphenicol in growth-limiting media are due primarily to an increase in the rate of initiation of new RNA chains, up to the rates existing in cultures growing rapidly in broth. Thus, in poorer media, only a small fraction of the available DNA-dependent RNA polymerase molecules are active at any given instant, since the chain-initiation rate is limiting in these conditions. In cultures growing rapidly in enriched broth, antibiotic inhibition caused a rise of some 12% in the rate of incorporation of exogenous uracil into total RNA. This small acceleration was due entirely to the partial stabilization of the mRNA fraction, which accumulated as 14% of the RNA formed after the addition of chloramphenicol. In cultures growing more slowly in glucose-salts or lactate-salts media, chloramphenicol caused an immediate acceleration of two- to three-fold in the overall rate of RNA synthesis. Studies by DNA-RNA hybridization showed that the synthesis of mRNA was accelerated in harmony with the other affected species. However, just over half the mRNA formed after the addition of chloramphenicol quickly decayed to acid-soluble products, whereas the remainder was more stable and accumulated in the cells. The mRNA fraction constituted about 6% of the total cellular RNA after 3h inhibition. A model was suggested to explain the partial stabilization and accumulation of the mRNA fraction and the acceleration in the rate of synthesis of mRNA when chloramphenicol was added to cultures in growth-limiting media.

Amino acid control over deoxyribonucleic acid synthesis in Escherichia coli infected with T-even bacteriophage

Starvation for a required amino acid of normal or RC(str)Escherichia coli infected with T-even phages arrests further synthesis of phage deoxyribonucleic acid (DNA). This amino acid control over phage DNA synthesis does not occur in RC(rel)E. coli mutants. Heat inactivation of a temperature-sensitive aminoacyl-transfer ribonucleic acid (RNA) synthetase similarly causes an arrest of phage DNA synthesis in infected cells of RC(str) phenotype but not in cells of RC(rel) phenotype. Inhibition of phage DNA synthesis in amino acid-starved RC(str) host cells can be reversed by addition of chloramphenicol to the culture. Thus, the general features of amino acid control over T-even phage DNA synthesis are entirely analogous to those known for amino acid control over net RNA synthesis of uninfected bacteria. This analogy shows that the bacterial rel locus controls a wider range of macromolecular syntheses than had been previously thought.

Continued expression of the ribonucleic acid control gene during inhibition of Escherichia coli ribonucleic acid and protein synthesis

The effect of the ribonucleic acid (RNA) control (RC) gene on the biosynthesis of viral RNA has been examined in an RC(str) and an RC(rel) host infected with R17 RNA bacteriophage under conditions in which host RNA and protein synthesis were inhibited by the addition of rifampicin. Methionine and isoleucine starvation depressed viral RNA biosynthesis in an RC(str) host but not in an RC(rel) host. However, histidine starvation had little effect on viral RNA and protein synthesis in both RC(str) and RC(rel) cells, although it had a marked effect on host protein and RNA synthesis in an RC(str) host. Chloramphenicol relieved the effect of amino acid starvation on viral RNA synthesis in an RC(str) host. It is concluded that stringent control of viral RNA biosynthesis does not require the continued biosynthesis of the RC gene product (RNA or protein) and that a preformed RC gene product can regulate the biosynthesis of the exogenous RNA. It is suggested that the amino acid dependence of viral RNA biosynthesis is due to its obligatory coupling with the translation of the viral coat protein which lacks histidine. It may be inferred that the amino acid requirement of bacterial RNA is due to its coupling with the translation of a host-specific protein (other than the RC gene product) which requires a full complement of amino acids. Since chloramphenicol is known to permit ribosome movement in the absence of protein synthesis, it is suggested that ribosome movement along the nascent RNA chain is a sufficient condition for the continuation of RNA synthesis.

Polysome stability in relaxed and stringent strain of Escherichia coli during amino acid starvation

The influence of amino acid starvation on polysome content was examined in relaxed and stringent strains of Escherichia coli which were isogenic for the RC locus. No difference was observed between the polysome profiles obtained from two different sets of stringent and relaxed strains starved for the same amino acid. In both relaxed and stringent strains, starvation for amino acids other than methionine resulted in only a slight breakdown of polysomes with a concomitant increase of 70S ribosomes. However, starvation for methionine in both RC stringent and relaxed strains of E. coli resulted in a more extensive degradation of polysomes and accumulation of 70S ribosomes. The 70S ribosomes obtained as a result of methionine starvation were more sensitive to degradation to 50 and 30S subunits in 10(-3)m Mg(2+) than 70S monomers obtained either by degradation of polysomes with ribonuclease or by starvation of cells for amino acids other than methionine. The 70S ribosomes from methionine starvation were similar (sensitivity to 10(-3)m Mg(2+)) to 70S ribosomes obtained from cells in which initiation of protein synthesis had been prevented by trimethoprim, an inhibitor of formylation. Since N-formyl-methionyl-transfer ribonucleic acid is required for initiation, the 70S ribosomes obtained in both methionine-starved and trimethoprim-treated cells must result from association of 50 and 30S subunits for reasons other than reinitiation. These results suggest that the level of ribonucleic acid synthesis does not influence the distribution of ribosomes in the polysome profile and vice versa.

Polyribosomes from Bacillus subtilis during amino acid starvation in the presence and in the absence of actinomycin

Polysomes were extracted from Bacillus subtilis cells starved for a required amino acid. The monosome peak appeared soon after starvation; no difference in the rate of degradation was detected when the cells were starved for arginine or tryptophan in a double auxotroph. RNA production during starvation was not inhibited by actinomycin, but the molecular weight of the product made in the presence of the antibiotic was much lower. Indications that stable messenger ribonucleic acid is present for up to 90 min after amino acid starvation are also presented.

Polysome-ribosome distribution in isogenic RC(str) and RC(rel) strains of Escherichia coli

Study of the relative proportions of ribosomes and polysomes released by a standardized lysing procedure from isogenic RC(str) and RC(rel) strains of Escherichia coli shows that a 20-min period of amino acid starvation of RC(str) bacteria reduces the fraction of ribosomes recovered in polysomes to about 60% of its value characteristic of exponentially growing cells: A similar starvation treatment of the RC(rel) bacteria causes no appreciable reduction in the fraction of polysomal ribosomes.

Properties of the inactive ribosomal components in rat liver and hepatoma

1. The relative concentrations of the inactive ribosomal components were compared in normal and regenerating rat liver and in two transplantable rat hepatomas (hepatomas 7800 and 5123D). 2. The size of the ribosomal-subunit pools in normal liver was not significantly affected by partial hepatectomy or neoplasia although, as shown previously, significant changes do occur in the monomer pool. 3. Further, the subunit pools in both liver and hepatoma were not significantly influenced by several treatments that caused dramatic changes in the size of the ribosomal monomer (and dimer) pools. 4. The high concentration of inactive monomers and dimers in the hepatomas appears to arise from limitations at the translational level, since they can be incorporated into pre-existing polyribosomes under the influence of cycloheximide.

Inhibitor-induced shift-downs in Escherichia coli

A shift-down response in Escherichia coli cells has been brought about by moderate concentrations of azide or cyanide. Early events of the response included a preferential inhibition of ribonucleic acid relative to deoxyribonucleic acid synthesis, a degradation of polyribosomes, and an inhibition of protein synthesis followed by a transient relief. These changes were entirely comparable to those observed with nutrient-induced shift-downs. The influences of various nutrient supplements on an azide shift-down were examined, and methionine was found to relieve effectively the inhibition of ribonucleic acid synthesis in some strains of cells.

Correlation between the rate of ribonucleic acid synthesis and the level of valyl transfer ribonucleic acid in mutants of Escherichia coli

By use of a mutant of Escherichia coli with a partially thermolabile transfer ribonucleic acid (tRNA) synthase, it was possible to regulate the rate of RNA synthesis over a 10-fold range. The addition of chloramphenicol to cultures kept at the nonpermissive temperature stimulated RNA synthesis. The longer the culture was kept at the nonpermissive temperature prior to addition of chloramphenicol, the lower was the resulting rate of RNA synthesis. The decrease in the rate of incorporation of labeled uracil into RNA was correlated with the decrease in the level of valyl tRNA. Additional experiments provided evidence which may be interpreted as indicating that valyl tRNA does not, by itself, react with the RNA-forming system.

Chloramphenicol and the stimulation of ribonucleic acid synthesis in Escherichia coli

Data have been obtained which imply that chloramphenicol stimulation of ribonucleic acid (RNA) synthesis is a result of the accumulation of aminoacyl transfer RNA (tRNA) molecules. The data also support the hypothesis that chloramphenicol exerts an additional effect upon the stimulation of RNA synthesis. This effect may be at the level of the ribosome or the aminoacyl tRNA, or of both. It is this effect combined with the presence of aminoacyl tRNA that results in stimulation by chloramphenicol of RNA synthesis.

Ribosomal precursors and ribonucleic acid synthesis in Escherichia coli

Ribosomes and immature ribonucleoprotein particles were isolated from extracts of log-phase cells grown under various conditions. Quantitative measurements were made to determine the relative amounts of immature particles present in the extracts. The results indicate that the steady-state level of ribosomal precursors accounted for essentially a constant fraction of the total ribonucleic acid (RNA) of the cells. For cells with RNA-protein ratios between 0.43 and 0.65, about 1.6% of the total RNA occurred as immature ribonucleoprotein particles. Further, increased levels of immature particles were shown to be correlated with a reduced rate of RNA synthesis in cells recovering from chloramphenicol inhibition. The reduction was found to vary directly with the duration of pretreatment in chloramphenicol and, consequently, with the level of immature particles present in the cells.

Physiology and genetics of the "ribonucleic acid control" locus in escherichia coli

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Ribonucleic acid synthesis in T2-infected Escherichia coli during "stringent" control

The leucine auxotroph Escherichia coli 2961 exhibited stringent control of net ribonucleic acid (RNA) synthesis during amino acid starvation. After leucine was exhausted from the medium, the rate of uracil incorporation into RNA rapidly decreased to 2 to 4% of the prestarvation value. Infection of the starved cells with T2 phage stimulated uracil incorporation to a level equivalent to that of unstarved, T2-infected cells. The RNA synthesized during leucine starvation of the T2-infected cells consisted of T2 and E. coli messenger RNA, but stable ribosomal RNA (23S and 16S) did not appear to be synthesized. It is concluded that one or more T2-specific proteins are required to shut off host messenger RNA synthesis. Furthermore, transcription of E. coli and T2 deoxyribonucleic acid is not necessarily coupled to the translation of messenger RNA during stringent control of net RNA synthesis.

Synthesis of bacterial flagella. I. Requirement for protein and ribonucleic acid synthesis during flagellar regeneration in Bacillus subtilis

A relatively simple immunochemical procedure for estimating flagellar protein was developed. This procedure involved measuring the binding of purified, radioactively labeled, antiflagellar antibodies to bacteria. The assay was used to determine the requirements for ribonucleic acid (RNA) and protein synthesis during flagellar regeneration in Bacillus subtilis. Immediate inhibition of flagella development was observed when chloramphenical or puromycin was added to cells. This inhibition indicated the absence of a large pool of flagella precursors that could be assembled in the absence of protein synthesis. When the cells were starved for uracil or treated with actinomycin D to inhibit RNA synthesis, the ability of the cells to regenerate flagella decayed with a half-life of 5.5 min. When B. subtilis auxotrophs were starved for tryptophan, they continued to synthesize flagella, although this process was also inhibited by actinomycin D. On the basis of these results, we concluded that (i) the system involved in flagellar regeneration does not have unusual metabolic stability, (ii) regeneration requires both concomitant protein and RNA syntheses, and (iii) B. subtilis continues to synthesize messenger RNA during tryptophan starvation.

Selection of temperature-sensitive activating enzyme mutants in Escherichia coli

A method based on temperature-conditional resistance to thymineless death has been designed to facilitate the isolation of amino acid-activating enzyme mutants. This method may be modified to obtain a greater or lesser proportion of activating enzyme mutants. In the latter instance, an increased proportion of temperature-sensitive macromolecule mutants of other types is obtained. Additional uses of this procedure are discussed.

Polyribosomes of growing bacteria

A method of extracting polyribosomes has been developed which uses lysozyme on bacteria in the exponential phase of growth. This procedure recovers more than 80 percent of the total ribonucleic acid and nearly all of the soluble protein. Analysis of the lysate on sucrose gradients shows that 80 to 90 percent of the ribosomes sediment with the polysome fractions, indicating little or no degradation. The method has been applied to both a Gram-positive and a Gram-negative organism under various growth conditions and has proved uniformly successful.

Isolation of ribosomes from pollen

Ribosomes have been isolated from lily pollen. The size distribution on sucrose gradients is similar to ribosomes from vegetative plant material. Some fractions in ungerminated pollen seem to be resistant to ribonuclease. With progressing germination the sucrose gradient profiles of ribosome preparations undergo changes, indicating changes in the translation process in correlation to a developmental process.ZUSAMMENFASSUNG: Aus Pollen von Lilien konnten Ribosomen isoliert werden. Das Profil am Zuckergradienten ist ähnlich dem Polysomen-Profil, wie es für vegetatives Pflanzenmaterial beschrieben ist. In ungekeimtem Pollen erscheinen einige Fraktionen besonders stabil gegenüber Ribonuklease. Mit fortschreitender Keimung ändert sich das Profil am Zucker-Gradienten. Dies kann als Ausdruck der Änderungen im Translation-Prozeß im Zusammenhang mit einem Entwicklungsprozeß angesehen werden.