Activation in Vitro of Rat Liver Polyribosomes

  • Published 2003


The increase in the incorporation of amino acids into protein in vitro by preparations obtained from protein-fed rats as compared with preparations obtained from carbohydratefed rats has been described previously . After molecular sieving through Sephadex G-25 of cell-free preparations, the difference in incorporating activity between the two types of rats was diminished in systems containing ATP, phosphoenolpyruvate, pyruvate kinase, GTP, and a mixture of amino acids. When, after molecular sieving, a mitochondrial (15,000 g) supernatant was incubated for 4 min at 35 °C the polysomal pattern of the preparations was unchanged . In the presence of ATP, phosphoenolpyruvate, and pyruvate kinase the polysomal incorporating activity was low and the polysomal pattern was only slightly changed. Addition of GTP increased the activity markedly, and a more pronounced activity was observed when a mixture of amino acids was added as well . As the amino acid incorporation ability increased, monosomes were formed from the polyribosomes . The activity of the polyribosomes was severalfold higher than that of non-Sephadex-treated preparations, indicating an activation of polysomal aggregates which under the usually applied conditions of incubation and prior to molecular sieving show little or insignificant activity . It was possible to activate polyribosomes from carbohydrate-fed and proteinfed rats to almost the same extent . incorporating activity of the system was observed (4, 5) . In addition, it was found that the cell sap contains components of high molecular weight that have an inhibitory effect on the incorporating activity (6, 7) . Thus it seems that a variety of components present in the cell sap influences the rate of protein synthesis. So far, it is not known which steps in protein synthesis are changed by the stimulatory and the inhibitory factors . The aim of this work is to study the activation process brought about by the stimulatory components. As will be shown below, the reactions of protein synthesis taking place at the polyribosomes are markedly enhanced . In fact, we will demonstrate an activation of those polyribosomal aggregates which under normal conditions show a depressed activity . on A ril 9, 2017 D ow nladed fom Published October 1, 1969

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@inproceedings{2003ActivationIV, title={Activation in Vitro of Rat Liver Polyribosomes}, author={}, year={2003} }