Effect of exogenous nucleotides on the candicidin fermentation

1977 ◽  
Vol 23 (10) ◽  
pp. 1334-1339 ◽  
Author(s):  
Juan F. Martin ◽  
Arnold L. Demain

Addition of cyclic-AMP (c-AMP) to Streptomyces griseus fermentations inhibited candicidin formation. In a phosphate-free resting cell system, c-AMP inhibited net candicidin formation and incorporation of labeled propionate and p-aminobenzoic acid into the antibiotic but did not inhibit protein synthesis. All nucleotides tested, regardless of the position of the phosphate ester, were effective inhibitors; nucleosides and free bases were not. Inhibition occurred whether the nucleotide was added early or late. The results indicate that inhibition of antibiotic formation by exogenous nucleotides, including cyclic nucleotides, is similar to the effect produced by inorganic phosphate.


1975 ◽  
Vol 152 (3) ◽  
pp. 583-592 ◽  
Author(s):  
J Mowbray ◽  
J A Davies ◽  
D J Bates ◽  
C J Jones

Perfused rat heart incorporated L-[14C]tyrosine into protein at a constant rate for up to 75 min. A purified bovine growth-hormone preparation (1 mug/ml) stimulated the incorporation to a new constant rate that was more than three times the control rate by 10 min after hormone addition to perfusate. The hormone, however, did not alter the intracellular tracer amino acid pool, and the relationship of this to the aminoacyl-tRNA precursor pool is discussed. It is concluded that the increased incorporation largely reflected a rapid increase in protein synthesis at the ribosomes. Measurements of cyclic nucleotide contents during the perfusion showed that these appeared to vary in a systematic way during the perfusion. This strands in contrast with the constant values given by several other parameters measured in this preparation. Futher, the cyclic nucleotide variation seems to be independent of external effectors. The steady-state performance of the heart correlates more closely the [cyclic AMP]/[cyclic GMP] ratio than with the content of the individual cyclic nucleotides. At 10 min after the addition of growth hormone a slight decrese in cyclic AMP content and a large decrease in cyclic GMP were found, suggesting that the hormone's effect in stimulating protein synthesis may be mediated by a decrease in cyclic nucleotide concentrations or an increase in the [cyclic AMP]/[cyclic |p] ratio. The findings are also consistent with an intracellularly directed role for these nucleotides, and the possibility that the cyclic nucleotide changes are an indirect result of growth-hormone action is discussed.



1981 ◽  
Vol 27 (10) ◽  
pp. 1044-1047 ◽  
Author(s):  
J. Terry ◽  
D. G. Springham

Intracellular and extracellular cyclic adenosine 3′, 5′-monophosphate (cyclic AMP) levels were measured during the growth of a streptomycin-producing strain of Streptomyces griseus. Increasing the inorganic phosphate concentration of the defined media resulted in a decreased streptomycin titre and alterations in the magnitude and timing of changes in cyclic AMP concentration. Addition of excess inorganic phosphate after 24 h of growth reduced steptomycin production but had no effect on the intracellular cyclic AMP concentration. The results do not suggest that the effect of inorganic phosphate on streptomycin biosynthesis is mediated by cyclic AMP.



1976 ◽  
Vol 81 (2) ◽  
pp. 495-506 ◽  
Author(s):  
A. Radvila ◽  
R. Roost ◽  
H. Bürgi ◽  
H. Kohler ◽  
H. Studer

ABSTRACT Lithium and excess iodide inhibit the release of thyroid hormone from preformed stores. We thus tested the hypothesis that this was due to an inhibition of thyroglobulin breakdown. Rats were pre-treated with propylthiouracil (PTU) for 3 weeks in order to deplete their thyroids of thyroglobulin. While the PTU was continued, lithium chloride (0.25 mEq./100 g weight) or potassium iodide (3 mg per rat) were injected every 12 h for 3 days. Thereafter the thyroglobulin content in thyroid gland homogenates was measured. PTU pre-treatment lowered the thyroglobulin content from 4.21 to 0.22 mg/100 mg gland. Lithium caused a marked re-accumulation of thyroglobulin to 0.60 mg/100 mg within 3 days. While iodide alone had only a borderline effect, it markedly potentiated the action of lithium and a combination of the two drugs increased the thyroglobulin content to 1.04 mg/100 mg. Thyroxine was injected into similarly pre-treated animals to suppress secretion of thyrotrophic hormone. This markedly inhibited the proteolysis of thyroglobulin and 1.3 mg/100 mg gland accumulated after 3 days. Excess iodide, given in addition to thyroxine, decreased the amount of thyroglobulin accumulated to 0.75 mg/100 mg gland. To study whether this could be explained by an inhibitory action of iodide on thyroglobulin biosynthesis, thyroid glands from animals treated with excess iodide were incubated in vitro in the presence of 0.2 mm iodide for 3 h. Iodide decreased the incorporation of radioactive leucine into total thyroidal protein and into thyroglobulin by 25 and 35 % respectively. Iodide did not inhibit protein synthesis in the kidney, liver or muscle tissue. Thus, large doses of iodide selectively inhibit thyroglobulin biosynthesis.





1983 ◽  
Vol 47 (7) ◽  
pp. 1649-1650
Author(s):  
Masahiro Ohsugi ◽  
Kayoko Miyauchi ◽  
Yasuko Inoue




Development ◽  
1965 ◽  
Vol 13 (3) ◽  
pp. 341-356
Author(s):  
F. S. Billett ◽  
Rosalba Collini ◽  
Louie Hamilton

In many bacterial systems chloramphenicol has been shown to inhibit protein synthesis (Hahn & Wisseman, 1951; Gale & Folkes, 1953). The precise mechanism of this inhibition is not clear, although the evidence suggests that the interaction of the soluble RNA-amino acid complex with the ribosomes is prevented because the attachment of the messenger RNA to the ribosomes is itself impaired (Lacks & Gros, 1959; Nathans & Lipman, 1961; Jardetsky & Julian, 1964; Julian & Jardetsky, 1964). In contrast to its effect on bacterial systems, chloramphenicol has been reported to have little or no action on the protein synthesis by cell-free extracts of mammalian cells (Rendi, 1959; Ehrenstein & Lipmann, 1961). A basis for this resistance has been proposed by Vazquez (1964), who finds that whereas bacterial ribosomes bind chloramphenicol, ribosomes from other organisms do not. Nevertheless, it cannot be stated with any confidence that chloramphenicol has no effect on the protein synthesis of animal cells.



1979 ◽  
Vol 35 (1) ◽  
pp. 253-266
Author(s):  
S.P. Gibbs

In 8 classes of algae, namely the Cryptophyceae, Raphidophyceae, Haptophyceae, Chrysophyceae, Bacillariophyceae, Xanthophyceae, Eustigmatophyceae and Phaeophyceae, the chloroplasts, in addition to being surrounded by a double-membraned chloroplast envelope, are also enclosed by a cisterna of endoplasmic reticulum called the chloroplast ER. Often this ER cisterna is continuous with the outher membrane of the nuclear envelope in such a manner that the nuclear envelope forms a part of the ER sac enclosing the chloroplast. In all these classes of algae except the Cryptophyceae, a regular network of tubules and vesicles, named the periplastidal reticulum, is present at a specific location between the chloroplast envelope and the chloroplast ER. In the Cryptophyceae, scattered vesicles are found between the chloroplast envelope and the chloroplast ER. Ribosomes which have been shown to be arranged to polysomes are found on the outer membrane of the chloroplast ER. It is proposed that nuclear-coded proteins which are destined for the chloroplast are synthesized on these polysomes, passing during synthesis into the lumen of the ER cisterna. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles then fuse with the outer membrane of the chloroplast envelope thereby delivering their contents to the lumen of the chloroplast envelope. Proteins then cross the inner membrane of the chloroplast envelope in an as yet unknown manner. Experimental evidence for this hypothesis comes from studies on Ochromonas danica using chloramphenicol and spectinomycin, which inhibit protein synthesis on plastid ribosomes, and cycloheximide, which inhibits protein synthesis on cytoplasmic ribosomes. In cells of Ochromonas exposed to chloramphenicol or spectinomycin, the periplastidal reticulum proliferates markedly becoming several layers thick. Presumably this build up of periplastidal reticulum occurs because the transport of cytoplasmically synthesized plastid proteins is slowed down when protein synthesis in the chloroplast is inhibited. Conversely, when cells of Ochromonas are treated with cycloheximide, there is a reduction in the amount of periplastidal reticulum presumably because there are no cytoplasmically synthesized proteins to be transported into the chloroplast.



FEBS Letters ◽  
1987 ◽  
Vol 212 (2) ◽  
pp. 317-322 ◽  
Author(s):  
Thomas Wagner ◽  
Martin Gross ◽  
Paul B. Sigler


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