B cell genomics behind cross-neutralization of SARS-CoV-2 variants and SARS-CoV

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Effect of protease inhibitors on protein degradation in rat hepatoma cells I. Effect on general protein degradation

Tosyllysine chloromethyl ketone and tosylphenylalanine chloromethyl ketone in vitro are active-site specific and irreversible inhibitors of trypsin (EC 3.4.21.4) and chymotrypsin (EC. 3.4.21.1) respectively. Using rat hepatoma cells in suspension culture, both inhibitors were found to partially inhibit breakdown of prelabelled cell proteins ot amino acids, the effect being greastest in the absence of serum. Protein synthesis in rat hepatoma cells, reticulocytes and reticulyte lysates was also irreversibly inhibited by these compounds. Reduction of ATP levels with antimycin a inhibited protein degradation, but neither tosylphenylalanine chloromethyl ketone nor tosyllysine chloromethyl ketone had any effect on ATP concentration in rat hepatoma cells. These results suggest that the degradation of at least some proteins in animal cells may involve the action of serine protease(s).     

Mitosis

Within the last decade, the study of mitosis has evolved into a multidisciplinary science in which findings from fields as diverse as chromosome biology and cytoskeletal architecture have converged to present a more cohesive understanding of the complex events that occur when cells divide. The largest strides have been made in the identification and characterization of regulatory enzymes (kinases and phosphatases) that modulate mitotic activity, as well as a number of the proteins and structural components (spindle, chromosomes, nuclear envelope) which carry out the mitotic instructions. One emerging theme appears to be that molecular signalling, which can involve modification of components (such as phosphorylation) or even their specific destruction, monitors the state of the mitotic cell at all stages. One of the major challenges for the future will be the identification of addititonal targets of the signalling machinery, as well as new regulatory components and their targets on the chromosomes, on the spindle, and at the cleavage furrow.