Thiophosphate labelling of mitochondria — Lack of evidence for an acyl-phosphate intermediate in oxidative phosphorylation

In the presence of substrate and oxygen, aurovertin-inhibited rat-liver mitochondria incorporate 0.27±0.02 nanomoles of [³⁵S] thiophosphate per mg protein into an acid-precipitable fraction. This incorporation is not prevented by uncouplers of oxidative phosphorylation. Furthermore, there is no significant difference in thiophosphate incorporation by aurovertin-or oligomycin-inhibited mitochondria. Since acyl-phosphate intermediates in other energy-transducing membrane systems are stable to acid precipitation and since acyl thiophosphates are anticipated to be more stable than acyl phosphates, these results support previous indications that acyl phosphates do not participate as intermediates in oxidative phosphorylation.