Abstract
The yeast C-8,7 sterol isomerase contains a polyvalent high-affinity drug binding site similar to mammalian sigma receptors. Exogenously supplied sigma ligands inhibit sterol biosynthesis in yeast, demonstrating a pharmacological relationship between sigma ligand-binding and C-8,7 sterol isomerase activity. We report the isolation of an Arabidopsis thaliana C-8,7 sterol isomerase by functional complementation of the corresponding sterol mutant in yeast and its characterization by exposure to sigma ligands. The yeast erg2 mutant, which lacks the C-8,7 sterol isomerase gene and activity, was transformed with an Arabidopsis cDNA yeast expression library. Transformed colonies were selected for restoration of C-8,7 sterol isomerase activity (i.e. wild-type ergosterol production) by enhanced resistance to the antibiotic cycloheximide. Sterols produced in complemented lines were characterized by gas chromatography-mass spectroscopy (GC-MS). The full-length A. thaliana cDNA (pA.t.SI1) that complemented the erg2 mutation contains an open reading frame encoding a 21 kDa protein that shares 68% similarity and 35% amino acid identity to the recently isolated mouse C-8,7 sterol isomerase. The sigma ligands, haloperidol, ifenprodil and verapamil inhibited the production of ergosterol in wild-type Saccharomyces cerevisiae and in the erg2 mutant complemented with pA.t.SI1. Structural and biochemical similarities between the A. thaliana C-8,7 sterol isomerase and the mammalian emopamil-binding protein (EBP) are discussed.
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Grebenok, R.J., Ohnmeiss, T.E., Yamamoto, A. et al. Isolation and characterization of an Arabidopsis thaliana C-8,7 sterol isomerase: functional and structural similarities to mammalian C-8,7 sterol isomerase/emopamil-binding protein. Plant Mol Biol 38, 807–815 (1998). https://doi.org/10.1023/A:1006028623875
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DOI: https://doi.org/10.1023/A:1006028623875