Disease relevance of FDX1

• Overexpression in Escherichia coli and affinity purification of chick kidney ferredoxin [1].
• The mRNA encoding the ferredoxin component is up-regulated by chronic vitamin D deficiency, which at the same time leads to sustained elevation in 1-hydroxylase activity; no short term effect of 1,25(OH)2D3 on ferredoxin mRNA in kidney cell culture could be demonstrated [2].

High impact information on FDX1

• As part of our interest in the kidney mitochondrial 1 alpha-hydroxylation of 25-hydroxyvitamin D3, we have constructed an expression plasmid coding for a fusion protein containing the chick kidney ferredoxin [1].
• The fusion protein possessed an absorption spectrum and an electron paramagnetic resonance spectrum quantitatively indistinguishable from those published for ferredoxin purified from adrenal glands and placenta or expressed in E. coli with another vector [1].
• The naphthoquinone menadione, which blocks electron transfer to the P450-associated enzyme, was the most effective inhibitor of the reaction in both intact cells (3 +/- 1% of basal expression; P < or = 0.002) and after reconstitution of HD-11 cell mitochondrial extracts with a ferredoxin, reductase, O2, and NADPH (5 +/- 1% of basal; P < or = 0.02) [3].
• Also, partially purified chick kidney mitochondrial cyclic AMP-stimulated protein kinase catalysed the phosphorylation of ferredoxin in vitro [4].
• We have used a cell-free rabbit reticulocyte translational system programmed with polyadenylated [poly(A)+] RNA prepared from chick kidney tissue to study the synthesis of nascent ferredoxin, a class of iron-sulphur-containing proteins functional in the renal mitochondrial 1 alpha- and 24-hydroxylases of 25-hydroxyvitamin D3 [4].

Biological context of FDX1

• Deduced amino acid sequence of mature chicken testis ferredoxin [5].
• In reconstitution experiments with ferredoxin-dependent NADPH-cytochrome c (P-450) reductase complexes, P-4501 alpha catalyzed the hydroxylation of 25-hydroxy-9,10-secocholesta-5,7,10(19)-trien-3 beta-ol at the C-1 position exclusively with a turnover number of 0.03 min-1 [6].
• Southern blot analysis of genomic DNA indicates that there is a single copy of the ferredoxin gene present in the chick genome [7].

Anatomical context of FDX1

• The cDNA sequence encoding the complete mature form of the steroidogenic ferredoxin from chicken testis has been determined and the amino acid sequence deduced therefrom has been compared with the sequences of bovine, human and porcine steroidogenic ferredoxins [5].
• A fraction solubilized from mitochondria by cholate became catalytically active in 1 alpha-hydroxylation of 25-hydroxyvitamin D3 after addition of ferredoxin and ferredoxin reductase [8].

Associations of FDX1 with chemical compounds

• [3H]Orotate incorporation as uridine into kidney poly(A)+ RNA was stimulated by aminophylline, a potent inducer of 25-hydroxyvitamin D3 24-hydroxylase; however, the amount of nascent ferredoxin synthesis was the same as in normal controls [4].
• Chick kidney mitochondrial 25-hydroxyvitamin D3 24-hydroxylase has been solubilized with sodium cholate and reconstituted with NADPH, beef adrenal ferredoxin, and beef adrenal ferredoxin reductase, each component being essential for maximal 24-hydroxylase activity [9].

Analytical, diagnostic and therapeutic context of FDX1

• The synthesis of ferredoxin was monitored by determining [35S]methionine incorporation into ferredoxin and quantified by SDS/PAGE and autoradiography after immunoprecipitation from the total translation products [4].
• Ferredoxin of 25-hydroxyvitamin D3-1alpha-hydroxylase. Anatomical distribution in the chick as determined by double-antibody radioimmunoassay [10].

References