Adrenodoxin

In mitochondria (Fig. lb), the electron acceptor protein is also a flavoprotein termed NADPH-adrenodoxin reductase (MW 50 kDa) because it was discovered in the adrenal cortex and because it donates its electrons not directly to the P450 but to the smaller redox protein adrenodoxin (MW 12.5 kDa). The two iron-sulphur clusters of this protein serve as electron shuttle between the flavoprotein and the mitochondrial P450. 

Kimura, T. Biochemical Aspects of Iron Sulfur Linkage in None-Heme Iron Protein, with Special Reference to Adrenodoxin . Vol. 5, pp. 1-40. 

Fig. 46. Schematic structure of the iron-sulfur complex in two-iron ferredoxin and adrenodoxin. (Adapted from Ref. 267)...

In 1971, adrenodoxin, an iron-sulfur protein with a single tyrosine residue and no tryptophan was shown to fluoresce at 331 nm upon 280-nm excitation at neutral pH/20 1 On cooling from room temperature to 77 K, the emission maximum shifts to 315 nm. The redox state of the iron does not have any effect on the tyrosine emission. From these results, an exciplex between the excited singlet state of tyrosine and an unidentified group was suggested as the cause of the anomalous emission energy/2031 Later studies have shown that the excitation spectrum is a red-shifted tyrosine spectrum, that removal of the iron to form the apoprotein has no effect on the emission, and that heat, low pH, guanidine hydrochloride, urea, and LiCl all cause the emission... 

T. Kimura and J. J. Ting, Anomalous tyrosine emission at 331 nm in adrenal two iron and two labile-sulfur protein (adrenodoxin) A possible tyrosine exciplex, Biochem. Biophys. Res. Commun. 45, 1227-1231 (1971). 

T. Kimura, J. J. Ting, and J. J. Huang, Studies on adrenal steroid hydroxylases. Anomalous fluorescence of a tyrosyl residue in adrenal iron-sulfur protein (adrenodoxin), J. Biol. Chem. 247, 4476-4479 (1972). 

B. T. Lim and T. Kimura, Conformation-associated anomalous tyrosine fluorescence of adrenodoxin,./. Biol. Chem. 255, 2440-2444 (1980). 

Mitochondrial inner membrane of pig and rabbit liver (Axen et al., 1994). Recombinant CYP27 requires adrenodoxin and adrenodoxin reductase (Pikuleva etal, 1997). 

Han S, Czernuszewicz RS, Kimura T, et al. 1989a. Fe2S2 protein resonance Raman revisited structural variations among adrenodoxin, ferredoxin, and red paramagnetic protein. J Am Chem Soc 111 3505-11. 

SULFATE ADENYLYLTRANSFERASE (ADP) ADRENODOXIN ADSORPTION ABSORPTION BIOMINERALIZATION MICELLAR CATALYSIS LANGMIUR ISOTHERM Adsorption coefficient LANGMUIR ISOTHERM Adsorption of gases,... 

RESONANCE RAMAN SPECTROSCOPY Ferredoxin-dependent enzymes, ADRENODOXIN BENZENE 1,2-DIOXYGENASE FERREDOXIN NADP REDUCTASE GLUTAMATE SYNTHASE HYDROGENASE... 

ACYL-CoA DEHYDROGENASES ADRENODOXIN ANTHRANILATE HYDROXYLASE AQUACOBALAMIN REDUCTASES... 

Adrenodoxin. Adrenodoxin is the only iron-sulfur protein which has been isolated from mammals. This protein from mitochondria of bovine adrenal cortex was purified almost simultaneously by Kimura and Suzuki (32) and Omura et al. (33). It has a molecular weight of 12,638 (34) and the oxidized form of the protein shows maximal absorbances at 415 and 453 nm. Adrenodoxin acts as an electron carrier protein in the enzyme system required for steroid hydroxylation in adrenal mitochondria. In this system, electron transfer is involved with three proteins cytochrome P. gQ, adrenodoxin and a flavoprotein. Reduced NADP gives an electron to Tne flavoprotein which passes the electron to adrenodoxin. Finally, reduced adrenodoxin transfers the electron to cytochrome Pas shown in Fig. 3. The mechanism of cytochrome P cq interaction with steroid, oxygen and adrenodoxin in mixed-function oxidase of adrenal cortex mitochondria has been reviewed by Estabrook et al. (35). 

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