The function of ABCG8 (ATP binding cassette subfamily G member 8, ENSG00000143921) is as follows. 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:15054092, PubMed:27144356). Required for normal sterol homeostasis (PubMed:11099417, PubMed:11452359, PubMed:15054092). The heterodimer with ABCG5 has ATPase activity (PubMed:16893193, PubMed:20210363, PubMed:27144356). {ECO:0000269|PubMed:11099417, ECO:0000269|PubMed:11452359, ECO:0000269|PubMed:15054092, ECO:0000269|PubMed:16893193, ECO:0000269|PubMed:27144356}.