Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / isolation & purification
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Adenosine Triphosphatases / metabolism*
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Electrophoresis, Polyacrylamide Gel
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Escherichia coli / genetics
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Escherichia coli / metabolism*
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Escherichia coli Proteins
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HSP40 Heat-Shock Proteins
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Heat-Shock Proteins / genetics
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Heat-Shock Proteins / isolation & purification
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Heat-Shock Proteins / metabolism*
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Kinetics
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Lactalbumin / metabolism
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Molecular Weight
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Protein Binding
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Structure-Activity Relationship
Substances
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DnaJ protein, E coli
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Escherichia coli Proteins
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HSP40 Heat-Shock Proteins
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Heat-Shock Proteins
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Lactalbumin
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Adenosine Triphosphatases