A role for a 70-kilodalton heat shock protein in lysosomal degradation of intracellular proteins

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Science  20 Oct 1989:
Vol. 246, Issue 4928, pp. 382-385
DOI: 10.1126/science.2799391


A 73-kilodalton (kD) intracellular protein was found to bind to peptide regions that target intracellular proteins for lysosomal degradation in response to serum withdrawal. This protein cross-reacted with a monoclonal antibody raised to a member of the 70-kD heat shock protein (hsp70) family, and sequences of two internal peptides of the 73-kD protein confirm that it is a member of this family. In response to serum withdrawal, the intracellular concentration of the 73-kD protein increased severalfold. In the presence of adenosine 5'-triphosphate (ATP) and MgCl2, the 73-kD protein enhanced protein degradation in two different cell-free assays for lysosomal proteolysis.

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