New ATP incorporating activities from rat liver mitochondria: the attachment of a portion of ATP to a pronase-sensitive receptor

Studies using a Brij 58 detergent extract of rat liver mitochondria reveal that these organelles can catalyze the time-dependent incorporation of a portion of ³H]ATP into an acid-insoluble product. The activities studied using 8 mM Mn⁺⁺ or 15 mM Mg⁺⁺ are stimulated by dithiothreitol and by CTP, GTP or UTP, while that studied using 2 mM Mg⁺⁺ is not. The incorporated tritium remains bound after incubation in the presence of excess unlabeled ATP and chromatography on Sephadex G-25. The labeled product is insensitive to ribonuclease A and snake venom phosphodiesterase, but is sensitive to pronase. The attached portion of the ATP molecule released upon treatment of the product has been tentatively identified as adenosine for the activities studied using 2 mM Mg⁺⁺ or 8 mM Mn⁺⁺ and as AMP (80%) and adenosine (20%) for the reaction studied using 15 mM Mg⁺⁺.