Self-degradation of heat shock proteins.

The 70-kDa heat shock protein of Drosophila decays in vivo at a much faster rate than other abundantly labeled proteins. Degradation also occurs in vitro, even during electrophoresis. It appears that this degradation is not mediated by a general protease and that the 70-kDa heat shock protein has a slow proteolytic action upon itself. Heat-induced proteins in CHO cells and a mouse cell line also degrade spontaneously in vitro, as do certain non-heat shock proteins from Drosophila tissues as well as the cell lines.