Interactions of calcium with yeast mitochondria.
The interactions of Ca2+ with mitochondria from Saccharomyces cerevisiae were explored. Mitochondria were loaded with the metallochromic dye Fluo-3 to measure the concentration of free calcium in the matrix. Addition of EGTA or Ca2+ led to fluctuations in mitochondrial free calcium between 120 and 400 nM. Ca2+ variations were slower at 4 degrees C than at 25 degrees C or in the presence of phosphate instead of acetate. The net uptake of 45Ca2+ was higher with phosphate than with acetate. The optimum pH for Ca2+ uptake was 6.8. Ruthenium red did not affect the uptake of Ca2+. Addition of antimycin-A or uncouplers led to a small and transient release of Ca2+. Addition of EGTA or the monovalent cations Na+ or K+ resulted in higher release of Ca2+. Site I but not site II dependent O2 consumption was partially inhibited by EGTA. The effect of Ca2+ on NADH oxidation is similar to results reported with enzymes from mammalian sources which use NADH, such as the pyruvate, isocitrate and oxoglutarate dehydrogenases.
Uribe
S
S
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México.
Rangel
P
P
Pardo
J P
JP
D000968:Antimycin A / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D009245:NADH Dehydrogenase / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D012441:Saccharomyces cerevisiae
D010710:Phosphates; D004533:Egtazic Acid; D000968:Antimycin A; D009245:NADH Dehydrogenase; D002118:Calcium