Description
ABCG5 (Atp-binding cassette, subfamily g, member 5) also known as STEROLIN 1, is a protein that in humans is encoded by the ABCG5 gene. The protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. This protein is a member of the White subfamily. The protein encoded by this gene functions as a half-transporter to limit intestinal absorption and promote biliary excretion of sterols. The ABCG5 gene contains 13 exons and spans about 28 kb. The ABCG5 gene is mapped on 2p21. It is expressed in a tissue-specific manner in the liver, colon, and intestine. This gene is tandemly arrayed on chromosome 2, in a head-to-head orientation with family member ABCG8. Mutations in this gene may contribute to sterol accumulation and atheroschlerosis, and have been observed in patients with sitosterolemia. Small (2003) reviewed the role of ABC transporters in secretion of cholesterol from liver into bile, particularly the role of ABCG5/ABCG8. The ABCG5 and ABCG8 genes are an example of closely neighboring genes in a head-to-head orientation that, when mutated, cause the same phenotype