Journal of Biological Chemistry · 1992 · 263 citations · 27 references
Life SciencesBiochemistryMolecular BiologyEnzymologyMolecular Cell BiologyProtein FoldingChaperone-assisted FoldingChaperone-mediated FoldingEnzyme FunctionEnzyme StabilityMolecular ChaperonesEukaryotic ChaperonesGel ElectrophoresisHsp70 Atp HydrolysisHsp70 Chaperone SystemMacromolecular Complex FormationNative Gel ElectrophoresisNative Polyacrylamide Gel ElectrophoresisUnfolded Protein Response
We report that a purified cytoplasmic Hsp70 homolog from Saccharomyces cerevisiae, Hsp70SSA1, exhibits a weak ATPase activity, which is stimulated by a purified eukaryotic dnaJp homolog (YDJ1p). Stable complex formation between Hsp70SSA1 and the permanently unfolded protein carboxymethylated alpha-lactalbumin (CMLA) was assayed by native gel electrophoresis. The affinity of Hsp70SSA1 for CMLA appeared to be regulated by YDJ1p. Significant reduction in both CMLA-Hsp70SSA1 complex formation and the release of CMLA pre-bound to Hsp70SSA1 was observed only in the presence of both YDJ1p and ATP. Thus, Hsp70SSA1 and YDJ1p interact functionally in the execution of Hsp70SSA1 chaperone activities in the eukaryotic cell.
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