[5][6] The protein is a 213 amino acids long, consisting almost entirely of a StAR-related transfer (START) domain.

It is also part of the StarD4 subfamily of START domain proteins, sharing 34% sequence identity with STARD4.

[8] Cholesterol homeostasis is regulated, at least in part, by sterol regulatory element (SRE)-binding proteins (e.g., SREBP1) and by liver X receptors (e.g., LXRA).

Upon sterol depletion, LXRs are inactive and SREBPs are cleaved, after which they bind promoter SREs and activate genes involved in cholesterol biosynthesis and uptake.

STAR is homologous to a family of proteins containing a 200- to 210-amino acid STAR-related lipid transfer (START) domain, including STARD5.