The peptide sequence DSYG(893–896) of the sheep sodium pumpa1 subunit is highly conserved among all K + -trans-porting P-type ATPases. To obtain information about its function, single mutations were introduced and the mutants were expressed in yeast and analysed for enzymatic activity, ion recognition, and a/bsubunit interactions. Mutants of Ser894 or Tyr895 were all active. Conservative phenylalan-ine and tryptophan mutants of Tyr895 displayed properties that were similar to the properties of the wild-type enzyme
