The State of ADP or ATP Fixed to the Mitochondria by Bongkrekate

The reported studies are intended to clarify the binding state of ADP fixed to mitochondria under the influence of bongkrekate, and thus to discern between the affinity increase and reorientation mechanism proposed for the bongkrekate effect. (a) The composition of the intramitochondrial adenine nucleotide pool is not changed under the influence of bongkrekate with and without added nucleotides. (b) The added ADP and ATP fixed by bongkrekate can be identified as AMP, ADP and ATP in the same proportions as in the endogenous pool. (c) The bound nucleotides respond to oxidative phosphorylation or uncoupler stimulated dephosphorylation similar as endogenous nucleotides. It can be concluded that the ADP or ATP fixed under the influence of bongkrekate to the mitochondria are equilibrated with the intramitochondrial adenine nucleotide pool and are active in intramitochondrial phosphate transfer reactions. The results disagree with the affinity increase mechanism but support the reorientation mechanism which postulates that ADP and ATP are trapped in the mitochondria under the influence of bongkrekate in the same amount as there are carrier sites available outside before bongkrekate addition.