Abstract
The ATP-binding cassette (ABC) transporter superfamily comprises
membrane proteins that efflux various substrates across extra- and
intra-cellular membranes. Mutations in ABC genes cause 21 human
disorders or phenotypes with Mendelian inheritance, including cystic
fibrosis, adrenoleukodystrophy, retinal degeneration, cholesterol, and
bile transport defects. Common polymorphisms and rare variants in ABC
genes are associated with several complex phenotypes such as gout,
gallstones, and cholesterol levels. Overexpression or amplification of
specific drug efflux genes contributes to chemotherapy multidrug
resistance. Conservation of the ATP-binding domains of ABC transporters
defines the superfamily members, and phylogenetic analysis groups the 48
human ABC transporters into seven distinct subfamilies. While the
conservation of ABC genes across most vertebrate species is high, there
is also considerable gene duplication, deletion, and evolutionary
diversification.
, 
