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Resolution of the ATP-Dependent Proteolytic System from Reticulocytes: A Component that Interacts with ATP

Avram Hershko, Aharon Ciechanover and Irwin A. Rose
Proceedings of the National Academy of Sciences of the United States of America
Vol. 76, No. 7 (Jul., 1979), pp. 3107-3110
Stable URL: http://www.jstor.org/stable/69938
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Resolution of the ATP-Dependent Proteolytic System from Reticulocytes: A Component that Interacts with ATP
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Abstract

The ATP-dependent proteolytic cell-free system from reticulocytes has been resolved into three components, each of which is absolutely required for acid solubilization of 125I-labeled bovine serum albumin radioactivity. In addition to the previously reported heat-stable polypeptide [Ciechanover, A., Hod, Y. & Hershko, A. (1978) Biochem. Biophys. Res. Commun. 81, 1100-1105], we now describe a protein of high molecular weight (≈ 450,000) that is labile at 42 degrees C. The extremely heat-labile factor is remarkably stabilized by ATP. GTP and CTP, which do not stimulate proteolysis, do not stabilize this factor. Adenylate nucleotides such as ADP or the nonhydrolyzable β ,γ imido or methylene analogues of ATP cause stabilization although they do not activate proteolysis. A third protein component of the protease system, stable at 42 degrees C, has been separated from the heat-labile species by salt precipitation. All three components are required with ATP for proteolytic activity, but thus far only the heat-labile factor has been shown to interact directly with ATP.

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