This is a family of integral membrane proteins, which may contain four transmembrane helices. Members of this family are thought to be involved in sterol C-4 demethylation. In S. cerevisiae they may tether Erg26p (sterol dehydrogenase/decarboxylase) and Erg27p (3-ketoreductase) to the endoplasmic reticulum or may facilitate interaction between these proteins [1]. The family contains a conserved arginine and histidine that may be functionally important.

1: A novel gene conserved from yeast to humans is involved in sterol biosynthesis. Gachotte D, Eckstein J, Barbuch R, Hughes T, Roberts C, Bard M; J Lipid Res 2001;42:150-154. PMID:11160377