ABCG5 and ABCG8 form an obligate heterodimer that mediates Mg(2+)- and ATP-dependent sterol transport across the cell membrane (PubMed:16352607, PubMed:16867993, PubMed:18402465). 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:12444248, PubMed:14504269, PubMed:14657202, PubMed:19846887, PubMed:25378657). Required for normal sterol homeostasis (PubMed:12444248, PubMed:14657202). The heterodimer with ABCG8 has ATPase activity (PubMed:16352607, PubMed:16867993). ATP + cholesterol(in) + H2O = ADP + cholesterol(out) + H(+) + phosphate ATP + H2O + sitosterol(in) = ADP + H(+) + phosphate + sitosterol(out) Cholesterol transport is inhibited by vanadate and by beryllium fluoride. Heterodimer with ABCG8. Detected in liver and jejunum (PubMed:12444248, PubMed:15040800, PubMed:18402465, PubMed:25378657). Detected on enterocyte villi (at protein level) (PubMed:15040800). Expressed in jejunum, ileum and, at lower level, in the liver (PubMed:11138003, PubMed:11907139, PubMed:11099417, PubMed:12444248, PubMed:25378657). Up-regulated in liver and small intestine by cholesterol feeding (PubMed:11099417). Up-regulated via the oxysterols receptor LXR/retinoic X receptor (LXR/RXR) pathway (PubMed:14657202). Endotoxin (LPS) significantly decreased mRNA levels in the liver but not in the small intestine (PubMed:12777468). 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 (PubMed:12208867, PubMed:12444248, PubMed:16867993, PubMed:15040800, PubMed:15054092, PubMed:18402465, PubMed:25378657). N-glycosylation is important for efficient export out of the endoplasmic reticulum (PubMed:15054092). A spontaneous mutation gives raise to thrombocytopenia and cardiomyopathy (trac), with recessive inheritance and fully penetrant phenotype. Mice are small, infertile, and have shortened lifespan. Mice deficient for both Abcg5 and Abcg8 appear healthy and are fertile, but display strongly increased levels of the food-derived plant sterols sitosterol and campesterol in liver and blood plasma (PubMed:12444248, PubMed:14657202, PubMed:25378657). When mice are fed chow containing 0.02% cholesterol, cholesterol levels in blood plasma and in liver are considerably lower than in wild-type (PubMed:12444248, PubMed:14657202). In spite of the increased plasma and liver levels of plant sterols, and the decreased cholesterol levels, the total sterol levels in plasma and liver are closely similar in wild-type and mutant mice (PubMed:14657202). When mice are fed chow containing 2% cholesterol, plasma cholesterol levels remain stable in wild-type, but increase 2.4-fold in mutant mice. In the liver of mice kept on chow containing 2% cholesterol, cholesterol levels increase 3-fold for wild-type mice and 18-fold for mutant mice, resulting in much higher cholesterol levels than in wild-type livers (PubMed:12444248). Dietary cholesterol absorption appears normal in mutant mice, but the absorption of dietary cholestanol, campesterol and sitosterol is increased (PubMed:12444248). At the same time, mutant mice have very low cholesterol levels in bile, suggesting that the increased hepatic cholesterol levels are due to impaired cholesterol secretion into bile (PubMed:12444248). Likewise, the levels of the food-derived plant sterols stigmasterol, sitosterol, campesterol and brassicasterol are strongly decreased in bile from mutant mice (PubMed:14657202). In contrast, biliary phospholipid and bile acid levels appear unchanged relative to wild-type (PubMed:12444248). The blood plasma of mice with liver-specific or intestine-specific disruption of Abcg5 and Abcg8 has nearly normal levels of cholesterol, and mildly increased levels of sitosterol and campesterol (PubMed:25378657). Mice with intestine-specific disruption of Abcg5 and Abcg8 have strongly increased levels of sitosterol and campesterol in enterocytes, similar to that observed for mice with complete gene disruption (PubMed:25378657). In addition, they display strongly increased levels of sitosterol and campesterol in bile (PubMed:25378657). Mice with liver-specific disruption of Abcg5 and Abcg8 have slightly increased levels of campesterol and sitosterol in the liver, and normal, low levels of sitosterol and campesterol in bile (PubMed:25378657). Enterocytes and liver from mice with liver-specific or intestine-specific disruption of Abcg5 and Abcg8 have normal cholesterol levels (PubMed:25378657). Belongs to the ABC transporter superfamily. ABCG family. Eye pigment precursor importer (TC 3.A.1.204) subfamily.