Interaction of Cytochrome C Oxidase with Steroid Hormones

Interaction of Cytochrome C Oxidase with Steroid Hormones

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Estradiol, testosterone and other steroid hormones inhibit cytochrome c oxidase (CcO) purified from bovine heart.The inhibition is strongly dependent on concentration of dodecyl-maltoside (DM) in the assay.The plots of Ki vs [DM] are linear for both estradiol Ubiquinol and testosterone which may indicate an 1:1 stoichiometry competition between the hormones and the detergent.Binding of estradiol, but not of testosterone, brings about spectral shift of the oxidized CcO consistent with an effect on heme a33+.

We presume that the hormones bind to CcO at the bile acid binding site described by Ferguson-Miller and collaborators.Estradiol is shown to inhibit intraprotein electron transfer between hemes a and a3.Notably, neither estradiol nor testosterone suppresses the peroxidase activity of CcO.Such a specific mode of action indicates that inhibition of CcO activity by the hormones is associated Bike Accessories - Mirrors with impairing proton transfer via the K-proton channel.