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Negative Feedback 2
Published in James E. Ferrell, Systems Biology of Cell Signaling, 2021
Activated ERK2 translocates to the nucleus, and transcription factors are prominent among the targets of active ERK2 (recall Figure 1.3), raising the possibility that ERK2-stimulated transcription might contribute to the termination of ERK2 signaling. One of the early clues that this is the case came from comparing responses to mitogenic signals in NIH 3T3 cells, a commonly studied mouse cell line, in the presence and absence of the protein synthesis inhibitor cycloheximide. In the absence of cycloheximide, cells responded to mitogens with a pulse of ERK2 activation, as expected, but in the presence of cycloheximide, the ERK2 activation went up and remained high (Figure 12.6a). This suggests that perhaps some protein whose mRNA is induced by mitogens is a negative regulator of ERK2 and that blocking its synthesis interfered with the normal deactivation of ERK2. Sure enough, one of the proteins upregulated by mitogens turned out to be a dual-specificity phosphatase that can dephosphorylate the activating threonine and tyrosine phosphorylations on the ERK2 proteins. This phosphatase, usually called MKP1 (for MAP kinase phosphatase 1) or DUSP1 (for dual-specificity phosphatase-1), is thought to play an important role terminating receptor tyrosine kinase signaling in NIH 3T3 cells.
Laboratory analysis of cyanobacterial toxins and bioassays
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Linda A. Lawton, James S. Metcalf, Bojana Žegura, Ralf Junek, Martin Welker, Andrea Törökné, Luděk Bláha
Cylindrospermopsin is a protein synthesis inhibitor, and as such, biological assays can be relatively slow and nonspecific. Therefore, the favoured assay is the cylindrospermopsin-specific ELISA kit. Several ELISA kits are commercially available for cylindrospermopsin with detection limits well below 1 µg/L, and these kits can be used directly on water samples. As the proportion of extracellular to cell-bound cylindrospermopsin can vary significantly, it is important to test for both the cell bound and free toxin. Use of kits will require relatively modest investment of a plate reader and the expense of the purchase of the kits. Full instructions for performing the assay, calibration and validation are provided with each kit. When establishing the use of ELISA, matching results with HPLC for selected samples and matrices will be valuable for determining the level of confidence as false positives have been shown with low-positive concentrations (Metcalf et al., 2017).
Lipase-Mediated Biocatalysis as a Greener and Sustainable Choice for Pharmaceutical Processes
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Monika Sharma, Tanya Bajaj, Rohit Sharma
Chloramphenicol (2,2-dichloro-N-[1,3-dihydroxy-1-(4-nitrophenyl)propan-2-yl] acetamide) is a broad-spectrum antibacterial belonging to the amphenicol class of antibiotics. It falls under the category of protein synthesis inhibitor drugs and has a bacteriostatic effect unless administered in high concentration. The increasing incidences of antibiotic resistance are leading to its administration in even higher doses and thus making the situation worse. The side effects of the drug include severe kidney and liver malfunction. Thus, the idea of using chloramphenicol derivatives seems to be more promising. The chloramphenicol esters can be produced by carrying out lipase-mediated esterification and transesterification of the hydroxyl groups of the drug. In one such study, Chloramphenicol palmitate was synthesized in the presence of Candida albicans lipase-B (CAL-B) and Thermomyces lanuginosus lipase (TLL). Chloramphenicol propionate has been synthesized (Fig. 1.19) with a recombinant strain of Bacillus amyloliquefaciens as the biocatalyst (Dong et al., 2017).
Low-cost multichannel system with disposable pH sensors for monitoring bacteria metabolism and the response to antibiotics
Published in Instrumentation Science & Technology, 2021
Cristina Ocaña, Sergi Brosel-Oliu, Natalia Abramova, Andrey Bratov
Finally, the effect of kanamycin on the E. coli bacteria was also tested. This antimicrobial agent is an aminoglycoside bactericidal antibiotic, which acts as a protein synthesis inhibitor.[17] As can be seen in Figure 4c, kanamycin effect can be noticed at concentrations starting from 1 µg/mL, which is lower than its minimum inhibitory concentration value (2 µg/mL).