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Palytoxin (PTX) induces a cation channel through interaction with Na+,K+-ATPase. It is unclear how this action relates to the enzyme catalytic activity. We examined whether the action of PTX depends on the catalytic domain specific for Na+,K+-ATPase. Wild-type Na+,K+-ATPase α-subunit (NNN) or its chimera (NCN), in which the catalytic domain was replaced with that of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase, was co-expressed with β-subunit in the yeast Saccharomyces cerevisiae. PTX (0.1–100 nM) increased K+ efflux in NNN- or NCN-transfected cells to a similar degree but not in non-transfected cells. When ouabain-resistant NNN and NCN were expressed, PTX also increased K+ efflux. Ouabain inhibited the effect of PTX in NNN or NCN cells but not in ouabain-resistant cells. These data suggest that the channel-forming action of PTX does not depend on the catalytic domain species. [Copyright &y& Elsevier]