This family consists of the fungal C-8 sterol isomerase and mammalian sigma1 receptor. C-8 sterol isomerase (delta-8--delta-7 sterol isomerase), catalyses a reaction in ergosterol biosynthesis, which results in unsaturation at C-7 in the B ring of sterols [1]. Sigma 1 receptor is a low molecular mass mammalian protein located in the endoplasmic reticulum [2], which interacts with endogenous steroid hormones, such as progesterone and testosterone [3]. It also binds the sigma ligands, which are are a set of chemically unrelated drugs including haloperidol, pentazocine, and ditolylguanidine [2]. Sigma1 effectors are not well understood, but sigma1 agonists have been observed to affect NMDA receptor function, the alpha-adrenergic system and opioid analgesia.

1: Isolation of the ERG2 gene, encoding sterol delta 8-->delta 7 isomerase, from the rice blast fungus Magnaporthe grisea and its expression in the maize smut pathogen Ustilago maydis. Keon JP, James CS, Court S, Baden-Daintree C, Bailey AM, Burden RS, Bard M, Hargreaves JA; Curr Genet 1994;25:531-537. PMID:8082205

2: Purification, molecular cloning, and expression of the mammalian sigma1-binding site. Hanner M, Moebius FF, Flandorfer A, Knaus HG, Striessnig J, Kempner E, Glossmann H; Proc Natl Acad Sci U S A 1996;93:8072-8077. PMID:8755605

3: Cloning and structural analysis of the cDNA and the gene encoding the murine type 1 sigma receptor. Seth P, Leibach FH, Ganapathy V; Biochem Biophys Res Commun 1997;241:535-540. PMID:9425306