Co-chaperone that binds to the molecular chaperone HSP82 and stimulates its ATPase activity. Binding to HSP82 promotes a conformational switch in the catalytic loop of HSP82, facilitating the interaction of the catalytic 'Arg-380' with ATP in the N-terminal nucleotide-binding domain. Although not essential, it confers thermotolerance when intracellular levels of HSP82 are limiting. Monomer. Interacts with HSP82. By heat shock. Present with 13939 molecules/cell in log phase SD medium. Belongs to the AHA1 family.