ABCG5 and ABCG8 form an obligate heterodimer that mediates Mg(2+)- and ATP-dependent sterol transport across the cell membrane (PubMed:27144356). Plays an essential role in the selective transport of dietary plant sterols and cholesterol in and out of the enterocytes and in the selective sterol excretion by the liver into bile (PubMed:11099417, PubMed:11138003, PubMed:27144356, PubMed:15054092). Required for normal sterol homeostasis (PubMed:11099417, PubMed:11138003, PubMed:15054092). The heterodimer with ABCG8 has ATPase activity (PubMed:16893193, PubMed:20210363, PubMed:27144356). ATP + cholesterol(in) + H2O = ADP + cholesterol(out) + H(+) + phosphate ATP + H2O + sitosterol(in) = ADP + H(+) + phosphate + sitosterol(out) The ATPase activity of the heterodimer is stimulated by cholate. Taurocholate, glycocholate, taurochenodeoxycholate, glycochenodeoxycholate and taurodeoxycholate also stimulate ATPase activity, but to a lower degree. Glycodeoxycholate has no significant effect on ATPase activity. ATPase activity is inhibited by vanadate and by berillium fluoride. Heterodimer with ABCG8. Strongly expressed in the liver, lower levels in the small intestine and colon. The Walker motif (consensus sequence G-X-X-G-X-G-K-[ST]-T) is expected to bind ATP. Within this motif, the conserved Lys is essential for transport activity mediated by the heterodimer with ABCG8. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the ABC transporter superfamily. ABCG family. Eye pigment precursor importer (TC 3.A.1.204) subfamily. Database for mutations in ABC proteins