N2 - Modeccin is shown to strongly inhibit the ability of HeLa cells to form colonies in vitro. In modeccin treated cells the rate of incorporation of labelled leucine was reduced earlier than that of uridine and thymidine, and the toxin also inhibited protein synthesis in a cell-free system from rabbit reticulocytes. When modeccin was added to human erythrocytes agglutination was induced upon subsequent addition of anti-modeccin indicating that the toxin binds to cell surfaces. This effect was strongly increased after neuraminidase treatment of the cells. Furthermore, neuraminidase treatment of HeLa cells strongly increased their sensitivity to modeccin. The data indicate that modeccin acts by binding to cell surfaces and then somehow interferes with protein synthesis.
M.PY - 1986/1/1Y1 - 1986/1/1N2 - The inhibition of protein synthesis in heme-deficient reticulocyte lysates is reversed by the addition of hemin (20 μM) or MgGTP (2 mM).
Protein synthesis Flashcards | Quizlet
N2 - The mammalian suprachiasmatic nucleus (SCN) has been identified as a circadian pacemaker. N-methyl-d-aspartate (NMDA), non-NMDA and substance P receptors have been suggested to be involved in handling of photic information in the SCN. In the Aplysia eyes, in which the circadian clocks are involved, serotonin- or cAMP-induced phase changes of the circadian rhythm were reported to be blocked by protein-synthesis inhibitors. Therefore, we investigated whether protein-synthesis inhibitor can block the non- NMDA receptor agonist (R,S)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide (AMPA)- or substance P (SP)-induced phase changes of SCN activity rhythm. Although application of 10 μM cycloheximide alone during the early part of the subjective night did not cause phase change, it blocked both 10 μM AMPA- and 1 μM SP-induced phase delay. The present result suggests that protein synthesis may be required in the manifestation of AMPA- and SP-induced phase change of circadian clock.
Protein Synthesis Inhibitors ~ Biology Exams 4 U
Cells of the immune system can induce the formation of fibrin; it has also been observed that small peptides derived by plasmic proteolysis of human fibrinogen and fibrin inhibit mitogen-stimulated blastogenesis and thymidine uptake in vitro by peripheral blood lymphocytes. In the present study, we demonstrate that early events, amino acid transport and protein synthesis, in the response of peripheral blood mononuclear cells to stimuli are inhibited by plasmic peptides of fibrinogen. Protein synthesis, assessed by incorporation of 3H-leucine into protein, was inhibited by the peptides but not by intact fibrinogen. At concentrations of 150 μg/culture, the peptides profoundly suppressed both basal and mitogen-stimulated protein synthesis. This inhibition was observed with exposure of the cells to the peptides for 4 hr or more and was not corrected by removal of the peptides. The transport of the nonmetabolizable amino acids α-aminoisobutyric acid, was suppressed by the peptides. Both the initial rate and maximum uptake of the amino acid into cells was inhibited by approximately 50%. When the total amount of 3H-leucine within the cells in the presence or absence of the peptides was normalized, 3H-leucine incorporation into protein was attenuated by 53% in the presence of peptides. These observations indicate that both amino acid transport and protein synthesis per se are affected. The fibrinogen-derived peptides neither inhibited the binding of phytohemagglutinin to the cells nor dissociated cell-bound mitogen. When the fibrinogen-derived peptides were subjected to molecular exclusion chromatography, only a single fraction was effective in the inhibition of both protein synthesis and thymidine uptake with similar specific activities, suggesting that a single peptide set may be responsible for the effects on both the early and late events of lymphocyte responses.
Inhibition of Protein Synthesis in Apoptosis - Cancer …
In primary hepatocyte cultures, maintained in a protein-free medium, streptomycin, penicillin, and Garamycin (gentamicin) all inhibited protein synthesis at concentrations above 0.1 m M. Some inhibition was also observed with the fungicide Mycostatin at 100 U/ml. Hepatocytic protein degradation was markedly inhibited by penicillin at concentrations above 0.1 m M, whereas streptomycin and Garamycin only showed slight inhibition at concentrations in excess of 1 m M. None of the antibiotics had any detectable effect on the structural integrity (viability) of the cells.