Participation of phosphoprotein in mitochondrial phosphorylating processes

The level and rate of [32Pi incorporation from orthophosphate into mitochondrial phosphoproteins and ATP has been studied in the presence of different oxidizable substrates (α-ketoglutarate, β-hydroxybutyrate, succinate) and inhibitors of oxidative phosphorylation (2-4-dinitrophenol, oligomycin, atractyloside). 1. 1. With α-ketoglutarate as substrate both oligomycin and 2,4-dinitrophenol are unable to abolish the incorporation of [32P]Pi into phosphoproteins, thus indicating that substrate-linked phosphorylation as well as respiratory chain phosphorylation is involved in this process. 2. 2. When β-hydroxybutyrate or succinate is the substrate, both 2,4-dinitrophenol and oligomycin abolish the incorporation of [32P]Pi into phosphoproteins. Atractyloside, however, while inhibiting the synthesis of ATP as effectively as does oligomycin, only slightly affects the labelling of phosphoproteins: this suggests that an energy-rich intermediate earlier than ATP can be responsible for [32P]Pi incorporation into mitochondrial phosphoproteins through respiratory chain phosphorylation. 3. 3. The equilibrium level of incorporation of [32P]Pi into phosphoproteins is closely dependent on the level of mitochondrial high-energy intermediates. In particular it is very likely that a direct transfer of phosphate from phosphoproteins to ADP occurs. © 1864.