| Abstract: | A yeast gene was found in which the derived protein sequence has similarity to human and bovine adrenodoxin reductase (Nobrega, F. G., Nobrega, M. P. and Tzagoloff, A. (1992). EMBO J. 11, 3821–3829; Lacour, T. and Dumas, B. (1996). Gene 174, 289–292), an enzyme in the mitochondrial electron transfer chain that catalyses in mammals the conversion of cholesterol into pregnenolone, the first step in the synthesis of all steroid hormones. It was named ARH1 (Adrenodoxin Reductase Homologue 1) and here we show that it is essential. Rescue was possible by the yeast gene, but failed with the human gene. Supplementation was tried without success with various sterols, ruling out its involvement in the biosynthesis of ergosterol. Immunodetection with a specific polyclonal antibody located the gene product in the mitochondrial fraction. Consequently ARH1p joins the small group of gene products that affect essential functions carried out by the organelle and not linked to oxidative phosphorylation. © 1998 John Wiley & Sons, Ltd. |
