Reduction and activity of cytochrome c in the cytochrome c-cytochrome aa3 complex.

An interaction between rat liver glucocorticoid--receptor complex and immobilized ATP was identified. Rat liver cytosol preparations were incubated with [3H]triamcinolone acetonide for 4 h at 4 degrees C and partially purified by precipitation with (NH4)2SO4 before use. The resulting glucocorticoid--receptor complex could be selectively adsorbed on to columns of ATP--Sepharose. The freshly prepared cytosol [3H]triamcinolone acetonide--receptor complex had very little affinity for binding to the ATP--Sepharose column, but acquired this ability on temperature- or salt-activation. The presence of 10 mM-sodium molybdate during this salt- or temperature-dependent activation blocked the binding of the receptor complex to ATP--Sepharose. The interaction is reversible, since it can be disrupted by high-salt conditions. A competitive binding assay, using free nucleotides in samples to be chromatographed, revealed a preferential interaction between ATP and the glucocorticoid--receptor complex. Buffer containing ATP was also used to elute the glucocorticoid--receptor complex from ATP--Sepharose columns successfully. When ATP was added to the preparations containing [3H]triamcinolone acetonide--receptor complexes, the steroid specificity or sedimentation properties of the complex remained unaltered. Our results demonstrate an interaction between rat liver glucocorticoid--receptor complex and immobilized ATP and suggest a role of this nucleotide in receptor function.