Required for homeostasis of heavy metal ions such as cadmium, cobalt and copper. Controls metal ion transport and prevents metal hyperaccumulation by negatively regulating the SMF1 and SMF2 metal transport systems. Under manganese-replete conditions facilitates trafficking of SMF1 and SMF2 metal transporters to the vacuole where they are degraded. Increased accumulation of copper, cadmium and cobalt ions and enhanced sensitivity to the toxic effects of copper and cadmium. Exhibits no additional sensitivity to manganese. SMF1 fails to enter the vacuole and is stabilized. Reverses the aerobic defects of yeast strains lacking superoxide dismutase (SOD). Concomitant deletion of SMF1 completely abolishes the ability of BSD2 deletion to suppress SOD deficiency and reverses the increased sensitivity to cadmium and copper. However cobalt ion hyperaccumulation is not suppressed. Present with 3070 molecules/cell in log phase SD medium. Belongs to the BSD2 family.