The human ATP-binding cassette (ABC) transporter superfamily

The transport of specific molecules across lipid membranes is an essential function of all living organisms and a large number of specific transporter s have evolved to carry out this function. The largest transporter gene fam ily is the ATP-binding cassette (ABC) transporter superfamily, These protei ns translocate a wide variety of substrates including sugars, amino acids, metal ions, peptides, and proteins, and a large number of hydrophobic compo unds and metabolites across extra- and intracellular membranes. ABC genes a re essential for many processes in the cell, and mutations in these genes c ause or contribute to several human genetic disorders including cystic fibr osis, neurological disease, renal degeneration, cholesterol and bile transp ort defects, anemia, and drug response. Characterization of eukaryotic geno mes has allowed the complete identification of all the ABC genes in the yea st Saccharomyces cerevisiae, Drosophila, and C. elegans genomes, To date, t here are 48 characterized human ABC genes. The genes can be divided into se ven distinct subfamilies, based on organization of domains and amino acid h omology. Many ABC genes play a role in the maintenance of the lipid bilayer and in the transport of fatty acids and sterols within the body. jlr Here, we review the current knowledge of the human ABC genes, their role in inhe rited disease, and understanding of the topology of these genes within the membrane.