Transfer RNA is an essential component of the ubiquitin- and ATP-dependent proteolytic system.
نویسندگان
چکیده
Protein degradation via the nonlysosomal ATP-dependent pathway in rabbit reticulocytes involves a number of components. In the initial event, ubiquitin, an abundant 76-residue polypeptide, becomes covalently linked to the protein substrate in an ATP-requiring reaction. Once marked in this way, the conjugated protein is proteolyzed in a reaction that also requires ATP. Ubiquitin-marking appears to be important to the progression of cells from one stage to another of the cell cycle; it may also be involved in gene activation. Here we show that tRNA is another essential component of the system. Ribonucleases strongly inhibit the ubiquitin- and ATP-dependent degradation of 125I-labeled bovine serum albumin in the reticulocyte system in vitro. RNAs extracted from fractions of the reticulocyte extract or from mouse cells restore proteolytic activity. When the RNA is fractionated by gel electrophoresis, only the tRNA fraction is active in restoring proteolysis. Furthermore, pure mouse tRNAHis, isolated by immunoprecipitation with patient autoimmune sera, restores the proteolytic activity. The possibility that the level of uncharged tRNA in mammalian cells regulates the ubiquitin- and ATP-dependent proteolytic system is discussed.
منابع مشابه
Transfer RNA is required for conjugation of ubiquitin to selective substrates of the ubiquitin- and ATP-dependent proteolytic system.
Degradation of intracellular proteins via the ubiquitin- and ATP-dependent proteolytic pathway involves several steps. In the initial event, ubiquitin, an abundant 76-residue polypeptide is covalently linked to the protein substrate in an ATP-requiring reaction. Proteins marked by ubiquitin are selectively proteolyzed in a reaction that also requires ATP. Ubiquitin conjugation to proteins appea...
متن کاملUbiquitin is the ATP-dependent proteolysis factor I of rabbit reticulocytes.
A small heat-stable polypeptide, ATP-dependent proteolysis factor 1 (APF-1), is an essential component of the ATP-dependent proteolytic system of rabbit reticulocytes (Ciechanover, A., Hod, Y., and Hershko. A. (1978) Biochem. Biophys. Res Commun. 81, 1100-1105). The following evidence supports the view that APF-1 is ubiquitin, a highly conserved heat-stable polypeptide found universally in natu...
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An endogenous inhibitor of the reticulocyte ATP-dependent proteolytic system has been purified partially by ammonium sulfate precipitation from rabbit reticulocyte and erythrocyte extracts. Inhibitor-free protease rapidly degrades 21-40% of the substrate [14C]methyl-alpha-casein per hour, resembling ATP-dependent activity in reticulocyte extracts. This proteolytic activity is not stimulated by ...
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Although protein breakdown in most cells seems to require metabolic energy, it has only been possible to establish a soluble ATP-dependent proteolytic system in extracts of reticulocytes and erythroleukemia cells. We have now succeeded in demonstrating in soluble extracts and more purified preparations from rabbit skeletal muscle a 12-fold stimulation by ATP of breakdown of endogenous proteins ...
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Previously, we isolated an ATP-dependent proteolytic pathway in muscle, liver, and reticulocytes that requires ubiquitin and the enzymes which conjugate ubiquitin to proteins. We report here that skeletal muscle contains another soluble alkaline energy-dependent (but ubiquitin-independent) proteolytic activity. The cleavage of non-ubiquitinated protein substrates by the partially purified prote...
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ورودعنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 82 5 شماره
صفحات -
تاریخ انتشار 1985