FDFT1 is a membrane-associated enzyme located at a branch point in the mevalonate pathway. The encoded protein is the first specific enzyme in cholesterol biosynthesis, catalyzing the dimerization of two molecules of farnesyl diphosphate in a two-step reaction to form squalene. Recombinant human FDFT1 protein, fused to His-tag at N-terminus, was expressed in E.coli .