Photoaffinity labeling of a mitochondrial hydrophobic protein by an anisotropic inhibitor of energy transduction in oxidative phosphorylation.

The monoazide derivative of ethidium, the parent compound of which is an anisotropic inhibitor of energy transduction in oxidative phosphorylation, was synthesized and shown to be useful as a photoaffinity probe. Results showed that monoazide ethidium specifically binds to a hydrophobic protein of mitochondria (with an apparent molecular weight of about 6200 in the presence of 0.1% sodium dodecyl sulfate). The molar binding ratios of monoazide ethidium to protein were about 5 and 17 with protein in the nonenergized and energized states, respectively. This protein differed from the dicyclohexylcarbodiimide-binding protein. We refer to this new hydrophobic protein, anisotropic inhibitor-binding protein, in this paper.