Biosynthesis of cholesterol represents one of the funda-mental cellular metabolic processes. SterolD14-reductase (D14-SR) is a microsomal enzyme involved in the con-version of lanosterol to cholesterol in mammals. Amino-acid sequence analysis of a 38-kDa protein puri®ed from bovine liver in our laboratory revealed 90% similarity with a human sterol reductase, SR-1, encoded by the TM7SF2gene, and with the C-terminal domain of human lamin B receptor.