The binding of 2′(or 3′)-O-(2,4,6-trinitrophenyl)adenosine 5′-triphosphate (TNP-ATP) to isolated bovine heart cytochrome c oxidase (COX) was studied by following its specific spectral change at 510 nm. The quantitative titration revealed two binding sites for TNP-ATP per monomer COX with a K d of 1.6 μM.
