ATP-binding cassette family

The ATP-binding cassette (ABC) family is a group of proteins which bind and hydrolyse ATP in order to transport substances across cellular membranes. They are prevalent in bacteria but are also in humans, and responsible for a diverse range of genetic diseases from Stargardt disease to Cystic Fibrosis.

Structure
ABC proteins have two nucleotide binding domains (areas where ATP binds to the protein and are hydrolysed to ADP) and two transmembrane domains (parts of the protein which span the membrane through which the substrate that's to be transported passes, the substrate translocation pathway).