ABCG5 and ABCG8 form an obligate heterodimer that mediates Mg(2+)- and ATP-dependent sterol transport across the cell membrane. Plays an essential role in the selective transport of the dietary cholesterol in and out of the enterocytes and in the selective sterol excretion by the liver into bile (PubMed:11099417, PubMed:11452359, PubMed:27144356, PubMed:15054092). Required for normal sterol homeostasis (PubMed:11099417, PubMed:11452359, PubMed:15054092). The heterodimer with ABCG5 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. Predominantly expressed in the liver (PubMed:11099417, PubMed:11452359). Low expression levels in the small intestine and colon (PubMed:11099417). Very low levels in other tissues, including brain, heart and spleen (PubMed:11452359). A functional Walker motif (consensus sequence G-X-X-G-X-G-K-[ST]-T) is expected to bind ATP. The essential Lys in this region is not conserved in ABCG8 (G-S-S-G-C-R-A-S) and is not required for transport activity mediated by the heterodimer with ABCG5. N-glycosylated. Disease susceptibility may be associated with variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Minor form detected in approximately 10% of the cDNA clones. Belongs to the ABC transporter superfamily. ABCG family. Eye pigment precursor importer (TC 3.A.1.204) subfamily. Seems to have a defective ATP-binding region. Database for mutations in ABC proteins