Mitochondrial Uptake of ^<45>Ca^<2+> Bound to Calcium-Binding Protein Isolated from Rat Liver Cytosol

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The mitochondrial uptake of ^<45>Ca^<2+> bound to calcium-binding protein newly isolated from rat liver cytosol was investigated. The binding of ^<45>Ca^<2+> to calcium-binding protein increased linearly with increasing amount of the protein. ^<45>Ca^<2+> bound to the binding protein was taken up by rat liver mitochondria and microsomes in the presence of 3mM adenosine 5'-triphosphate (ATP) in the incubation medium, while the uptake was slight in the absence of ATP. The mitochondrial uptake of ^<45>Ca^<2+> bound to the binding protein started within 15s of the start of incubation and was saturated at 5min. The amount of ^<45>Ca^<2+> taken up by the mitochondria from ^<45>Ca^<2+>-binding protein increased linearly with increasing concentration of the protein-bound ^<45>Ca^<2+>. The mitochondrial uptake of ^<45>Ca^<2+> from the binding protein was markedly inhibited by the presence of mitochondrial calcium uptake inhibitors, ruthenium red (10μM), lanthanum chloride (250μM), and oxidized form of nicotinamide adenine dinucleotide (NAD^+ ; 2.5mM). The present results suggest that the cytosolic calcium-binding protein binds calcium ion in rat liver cytosol and the metal is subsequently transported into the organelles. This protein may play a role in the regulation of the cytosolic calcium ion level.
公益社団法人日本薬学会の論文
1985-08-25