Japanese flounder (Paralichthys olivaceus) Hsp70: Adjuvant effect and its dependence on the intrinsic ATPase activity

► An flounder Hsp70 homologue, PoHsp70, exhibited ATPase activity as a recombinant protein. ► PoHsp70M, which bears mutation of the ATPase domain, was abolished in activity. ► Expression of PoHsp70 was induced by vaccination with a DNA vaccine. ► PoHsp70 and PoHsp70M were each co-expressed with a DNA vaccine. ► PoHsp70, but not PoHsp70M, significantly increased the protection of the DNA vaccine.