Mg2+, Ca2+, Co2+, and Mn2+ influx into yeast mitochondria. The medium contained 0.3 M KCl, 10 mM HEPES, pH 7.2, and 0.1 mM decavanadate (Na+). Either 4 mM MgCl2, MnCl2, CoCl2, or CaCl2 were present as indicated. EGTA (K+) was present at different concentrations to yield the indicated free divalent cation concentrations as described in Methods. The mitochondria were incubated for 5 min. in the indicated free ion concentration, then spun down for 2 minutes in a microcentrifuge, washed once with a cold solution containing 0.6 M mannitol, 10 mM MES (TEA+), pH 6.0, and then spun down again. Ion concentrations were then determined as described in Methods.