Components of the Electron Transport System in Adrenal Steroid Hydroxylase: ISOLATION AND PROPERTIES OF NON-HEME IRON PROTEIN (ADRENODOXIN)

Abstract

Components of the electron transport system involved in steroid 11β-hydroxylation in pig adrenal cortex are a flavoprotein (adrenodoxin reductase), a non-heme iron protein (adrenodoxin), and possibly cytochrome P450. Reconstitution of reduced nicotinamide adenine dinucleotide phosphate cytochrome P450 reductase was achieved from soluble components. Adrenodoxin contains 2 iron atoms and 2 moles of labile sulfide per mole, has a molecular weight of approximately 20,000, and has a high oxidation-reduction potential. The iron atoms, which are ferric in the oxidized form, play a dual role: as a chromophore and as a center of asymmetry. Upon reduction, the environment of the iron of adrenodoxin is changed greatly as judged by spectral and optical rotatory properties.