Induction of vacuolar Ca 2-ATPase and H / Ca 2 exchange activity in yeast mutants lacking Pmr 1 , the Golgi Ca 2-ATPase

We have analyzed Ca2‡ transport activity in defined subcellular fractions of an isogenic set of wild-type and mutant yeast. The results, together with measurements of polypeptide expression levels and promoter: :reporter gene activity, show that the Golgi Ca2‡-ATPase, Pmr1, is the major Ca2‡ pump under normal growth conditions. In the absence of Pmr1, we show a massive, calcineurin-dependent compensatory induction of the vacuolar Ca2‡-ATPase, Pmc1. In addition, H‡/Ca2‡ exchange activity, that may be distinct from the vacuolar exchanger Vcx1, is also increased. z 1999 Federation of European Biochemical Societies.