Induction of vacuolar Ca2+-ATPase and H+/Ca2+ exchange activity in yeast mutants lacking Pmr1, the Golgi Ca2+-ATPase

We have analyzed Ca2+ transport activity in defined subcellular fractions o f 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 und er normal growth conditions. In the absence of Pmr1, we show a massive, cal cineurin-dependent compensatory induction of the vacuolar Ca2+-ATPase, Pmc1 , In addition, H+/Ca2+ exchange activity, that may be distinct from the vac uolar exchanger Vcx1, is also increased. (C) 1999 Federation of European Bi ochemical Societies.