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 Saccharomyces cerevisiae (Baker's yeast) they may tether Erg26p (sterol dehydrogenase/decarboxylase) and Erg27p (3-ketoreductase) to the endoplasmic reticulum or may facilitate interaction between these proteins []. The family contains a conserved arginine and histidine that may be functionally important.
