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Biomedical subjects

J D Friesen

Publications and source records attributed to J D Friesen.

At least 109 records · Page 6Linked to original sources
PubMed1976

A transducing bacteriophage lambda carrying the structural gene for elongation factor Ts.

A specialized transducing bacteriophage lambdadpolCdap D-9 has been isolated that carries the structural gene for EF-Ts1 (tsf). The presence of EF-Ts among the proteins synthesized under the direction of this phage in UVL-inactivated cells has been detected by two-dimensional gel electrophoresis and has been verified by antibody precipitation. In an induced lysogen of this phage the relative rate of synthesis of EF-Ts is increased 4-fold. Evidence is presented which suggest that the structural genes for ribosomal protein S2 (rpsB) and RNA polymerase sigma factor (sit) also lies on lambdadpolCdap D-9.

Coliphages↗
PubMed1976

A relaxed mutant with an altered ribosomal protein L11.

Relaxed mutants of Escherichia coli have been isolated which have an altered electrophoretic mobility of ribosomal protein L11. It can be shown that reversion to stringency in one of these mutants occurs simultaneously with a reversion of L11 protein to tis normal mobility. The L11 structural gene, rplK, maping near rif, is carried by the bacteriophage lambdacI857S7drifd18, and is most likely identical with relC.

Bacterial Proteins↗
PubMed1976

Isolation of transducing phage carrying rps T, the structural gene for ribosomal protein S20.

Lambda transducing phages carrying segments of the Escherichia coli chromosome in the dapB region have been isolated in their in vivo gene products analyzed by two-dimensional gel electrophoresis. One of these phages, lambdaddapB-2, carries the structural genes for ribosomal protein S20 (rps T) and isoleucyltransfer RNA synthetase (ileS.) The most likely gene order is thr-rpsT-ileS-dapB-pyrA.

Bacterial Proteins↗
PubMed1976

A mutant of Escherichia coli with an altered elongation factor Tu.

A previously isolated mutant of E. coli K12 HAK 88 [Kuwano, M., Endo, h & yamamoto, M. (1972) J. Bacteriol, 112, 1150-1156], contains a new protein that in two-dimensional gel electropherorgrams has the same molecular weight as normal elongation factor Tu, but whose isoelectric point is altered approximately 0.1 pH unit in the acidic direction. Peptide mapping, purification properties and the ratio of leucyl plus isoleucyl to methionyl plus cysteinyl residues of the normal elongation factor Tu protein and the new protein show a close similarity between the two. The mutation causing the altered electrophoretic mobility is located between argH and rif (79 min on the E. coli genetic map). These biochemical and genetic data indicate that strain HAK 88 has a mutationally altered tufB gene.

Chromosome Mapping↗
PubMed1976

Isolation of a lambda transducing bacteriophage carrying the relA gene of Escherichia coli.

In Escherichia coli the relA and pyrG loci are 99% cotransducible. On the basis of this knowledge, we have isolated lambdacI857S7dpyrG transducing bacteriophages carrying both the pyrG and relA genes. Single lysogens of this bacteriophage show basal levels of ppGpp that are 10-fold higher than normal. Stringent factor is present among the gene products synthesized by lambdadpyrG relA after infection of ultraviolet-killed cells, as analyzed by polyacrylamide gel electrophoresis. The intracellular content of stringent factor, as determined by enzymatic activity, rises 20-fold after induction of a single lysogen of lambdadpyrG relA. As measured by two-dimensional gel electrophoresis, the amount of stringent factor in an exponentially growing strain carrying a pyrG relA plasmid is at least 10-fold greater than in a normal strain. These data constitute strong evidence that stringent factor is the relA gene product.

Amino Acids↗
PubMed1975

Synthesis and turnover of basal level guanosine tetraphosphate in Escherichia coli.

Cultures of escherichia coli growing exponentially in Trisacetate medium were subjected to nutritional shift-up and the pool size of guanosine 5'-3'-diphosphate-3'diphosphate (ppGpp) as well as the rates of protein synthesis and net RNA synthesis were determined. In the shift to a rich medium (glucose plus 19 amino acids plus hypoxanthine) the basal level of ppGpp falls immediately with a decay constant suggesting total inhibition of synthesis; ther is no ppGpp detectable above background for 30 to 40 min. The net rate of RNA synthesis starts to increase within 1 min of the shift-up and has reached its definite postshift value well before the pool of ppGGpp rises above background lvel. In a shift-up from Tris-acetate medium to Tris-glucose medium there is a much slower readjustment of the ppGpp pool size without the transient disappearance of the nucleotide. However, in a shift-up to Tris-acetate plus 5 amino acids, a medium which supports the same growth rate as Tris-glucose medium, a dramatic, transient drop in the ppGpp pool level was observed. Relaxed cells exhibit very similar behavior to strigent cells in the same shift-up. Our data argue strongly against an exclusive role for pGpp in regulating RNA synthesis during niutritional shift-up. The kinetic data of [3H]guanosine uptake into GTP and ppGpp pools were analyzed to determine the rate of pGpp synthesis. This rate was found to be similar during expotential growth in either Tris-acetate medium. During a shift-down from Tris-glucose to Tris-acetate medium the rate of ppGpp syntesis fell by a factor of 1.5 to 2 and the turnover rate is reduced 6- to 8-fold, suggesting that the expansion in the ppGp pool during shift-down canot be due to derepression of synthesis.

Bacterial Proteins↗
PubMed1975

New chromosomal location for structural genes of ribosomal proteins.

An Escherichia coli mutant, ts9, previously reported by Flaks et al. (Cold Spring Harbor Symp. Quant. Biol. 31, 623-631, 1966) to have an electrophoretically altered ribosomal protein, has been further characterized and the altered component has been identified as L7/L12. Although mutant ts9 is temperature sensitive for growth (rts-), the rts and L7/L12 mutations are genetically separable and are both located between argH and rif. The L7/L12 mutation (rpyL) maps very close to relC, mutants of which have a defect in the 50S ribosomal subunit. The gene order is argH-rts-(rpyL,relC)-rif. Protein synthesis directed by bacteriophage lambdacI857S7drifd18 in ultraviolet-irradiated cells indicates that L7/L12, As well as L1, L10, L11, and possibly L8 or L9 are coded by the phage DNA. Our results indicate that rpyL is the structural gene for L7/L12 and that this region of the E. coli chromosome contains a cluster of structural genes for ribosomal proteins.

Bacterial Proteins↗
PubMed1975

Cellular content of ribonucleic acid and protein in Saccharomyces cerevisiae as a function of exponential growth rate: calculation of the apparent peptide chain elongation rate.

The average cellular content of ribonucleic acid and protein was determined in cultures of Saccharomyces cerevisiae growing exponentially at different rates in a variety of media. Estimations of the proportion of total cellular ribonucleic acid that is made up of ribosomal ribonucleic acid were used to calculate the average number of ribosomes per cell at the different growth rates. The fraction of ribosomes actively engaged in translation was estimated by sucrose gradient centrifugation of ribosomes and polysomes. These data were used in a calculation of the apparent time taken for the addition of an amino acid to the growing polypeptide chain; this value was found to vary linearly with growth rate over a fivefold range of doubling times.

Adenine↗
PubMed1975

The effect of hemicholinium-3 on choline and acetylcholine levels in a sympathetic ganglion.

Pregangliaaonic stimulation of the cat's superior cervical ganglion in the presence of hemicholinium-3 (HC-3) produced the expected depletion of acetylcholine (ACh) stores, but failed to cause a corresponding reduction in the choline content. These results suggest that either HC-3 possesses an intracellular site of action or that in lower doses it selectively inhibits a specialized choline transport system in cholinergic nerves. At a dose of 2 mg/kg, HC-3 probably blocked ACh synthesis completely in ganglia stimulated at 20 Hz. Under these conditions, there was a rapid depletion of ACh to about 50% of control levels during the first 5 min of stimulation and thereafter the rate of decline in ACh levels proceeded at a much slower pace. Since the 2 mg/kg dose of HC-3 did not raise plasma choline concentrations, it may be assumed that non-specialized choline transport systems in other tissues were not significantly inhibited by this dose of HC-3. However, when the dose of HC-3 was increased to 4 mg/kg, plasma choline levels increased by 58%.

Acetylcholine↗
PubMed1974

A new relaxed mutant of Escherichia coli with an altered 50S ribosomal subunit.

A new relaxed mutant called rel C has been isolated from a rel A(+)/rel A(+) partial diploid strain. The rel C mutant is unable to synthesize ppGpp or pppGpp in vivo in response to amino acid starvation or in vitro, but can synthesize these nucleotides in a shift-down. Rel C maps near rif. Studies in vitro demonstrate the lesion to be probably in one of the 50S ribosomal proteins that can be removed by 1.0 M LiCl.

Amino Acids↗
PubMed1973

Accumulation of guanosine tetraphosphate in T7 bacteriophage-infected Escherichia coli.

Accumulation of guanosine tetraphosphate (ppGpp) in Escherichia coli strain AS19 valS, carrying a temperature-sensitive valyl-transfer ribonucleic acid synthetase and infected with bacteriophage T7, was studied. Valine starvation was achieved by culturing this strain at 42 C. Addition of rifampin to an uninfected culture at the nonpermissive temperature resulted in loss of accumulated ppGpp; however, cultures infected with phage T7, treated with rifampin, and then shifted to the nonpermissive temperature maintained the ability to accumulate ppGpp. Moreover, treatment of the T7-infected culture with rubidomycin, an antibiotic which inhibits transcription, did not reduce the amount of ppGpp accumulated following shift to the nonpermissive temperature. Measurements of the instantaneous rate of T7 transcription showed that it is not under stringent control of amino acids. ppGpp synthesized in T7-infected E. coli appears to be more stable than its counterpart in an uninfected culture. These results are interpreted to mean that ppGpp production is not directly dependent on transcription and arises instead from inhibition of another reaction, most likely some aspect of translation.

Adenine↗
PubMed1973

Inhibitors of ribonucleic acid synthesis in Saccharomyces cerevisiae: decay rate of messenger ribonucleic acid.

Daunomycin and ethidium bromide, two deoxyribonucleic acid-intercalating drugs, inhibit ribonucleic acid (RNA) and protein synthesis in Saccharomyces cerevisiae. Both agents rapidly curtail uptake of radioactive adenine, whereas the kinetics of radioactive leucine uptake after drug addition are consistent with translation of a pool of exponentially decaying messenger RNA. Messenger RNA half-life determinations from these experiments gave identical results over a range of drug concentrations; this value is 21 +/- 4 min at 30 C. In a temperature-sensitive mutant in which RNA synthesis is curtailed at the nonpermissive temperature, a similar half-life for messenger RNA decay is found both in the absence and in the presence of either drug. This indicates that at the concentrations used in this study, neither daunomycin nor ethidium bromide has an appreciable direct effect on translation and do not increase the lability of messenger RNA.

Adenine↗
PubMed1969

Amino acid regulation of messenger ribonucleic acid synthesis in T4-infected Escherichia coli.

The effect of amino acid starvation on the synthesis of T4 messenger ribonucleic acid (mRNA) was studied by measuring the uptake of labeled precursors into Escherichia coli cells which were infected prior to amino acid starvation. The results indicated that the rate of uptake of labeled uracil and adenine into T4 mRNA was reduced by approximately 50% when amino acids were withheld from stringent K-12 strains, but not when they were withheld from a stringent strain B or a relaxed strain K-12. Chloramphenicol reversed the inhibition of precursor uptake resulting from amino acid starvation in the RC(str) K-12 strain. Pulse-labeling experiments reinforced these observations. Pulse-decay experiments in conjunction with actinomycin D indicated that the observed pattern of precursor uptake was probably not due to differences in mRNA decay rate. It is concluded that if amino acids exert any direct effect on the synthesis of T4 mRNA such an effect is much smaller than that observed for bulk RNA synthesis in the uninfected cell. These experiments also indicated that actual translation of the genetic message is not necessary for its transcription.

Adenine↗