Evidence for the cluster model of mitochondrial steroid hydroxylase system derived from dissociation constants of the complex between adrenodoxin reductase and adrenodoxin.
Using biotinylated adrenodoxin and avidin-Sepharose 4B, dissociation constants for the complex between adrenodoxin reductase and adrenodoxin in the oxidized and reduced states were determined as 50 +/- 11 and 296 +/- 44 nM, respectively. Concentrations of adrenodoxin reductase/adrenodoxin in the matrix fraction from bovine adrenal cortex, liver, and kidney mitochondria were determined to be 20.2 +/- 10.6 microM/120 +/- 23 microM, 0.17 +/- 0.06 microM/1.79 +/- 0.24 microM, and 0.40 +/- 0.23 microM/1.33 +/- 0.26 microM, respectively. The calculation of the percentage of adrenodoxin reductase in the complex form in the reduced state showed that it is higher than 99% in adrenal cortex mitochondria, providing clear evidence for the cluster model for the mitochondrial steroid hydroxylase system.
Hara
T
T
Department of Biochemistry, Graduate School of Health and Nutrition Sciences, Nakamura Gakuen University, 5-7-1 Befu, Jonan-ku, Fukuoka, 814-0198, Japan. thara@cc.nakamura-u.ac.jp
Koba
C
C
Takeshima
M
M
Sagara
Y
Y
D000325:Adrenodoxin / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*
D000325:Adrenodoxin; D013250:Steroid Hydroxylases; D005287:Ferredoxin-NADP Reductase