Elevated cytosolic free Ca2+ concentrations and massive Ca2+ accumulation within vacuoles, in yeast mutant lacking PMR1, a homolog of Ca2+ -ATPase.

The Ca2+ -ATPase homolog of Saccharomyces cerevisiae, PMR1, cloned by Rudolph et al. (Cell 58 (1989) 133-145) is required for normal Golgi functions. We have investigated the role of Pmr1-protein in maintaining homeostasis of cytosolic free Ca2+ concentration ([Ca2+]i). It was found that exposure to moderately high Ca2+ concentrations led to elevated levels of [Ca2+]i in cells of pmr1 null mutant, in comparison with cells of pmr2 isogenic mutant (defective in cell-membrane Na+ - ATPase) and of an isogenic wild type. In addition, we showed that PMR1 deletion causes massive accumulation of Ca2+ in the vacuoles and affects the rates of Ca2+ influx and efflux.