The ATP-binding cassette (ABC) genes constitute one of the largest super-families in living organisms. The majority of ABC proteins encode membrane proteins that utilize the energy of ATP binding and hydrolysis to transport a diverse set of compounds. ABC systems are critical to the cellular physiology of prokaryotes, facilitating the import of nutrients, the extrusion of toxins and for DNA repair.

In eukaryotes, ABC proteins function primarily as efflux pumps (or as import pumps in intracellular organelles) playing important roles in protecting organisms from xenobiotics, antigen presentation, cholesterol and lipid transport. As ABC transporters extrude an unusually large set of chemically diverse compounds, they impede the treatment of microbial infections and human cancers and are implicated in multidrug resistance (MDR).

Among prokaryotes, ABC proteins segregate into 29 families belonging to three main classes approximating the functional divisions of the ABC system (importers, exporters and "other").

from Zuben E. Sauna and Suresh V. Ambudkar (2009) in ABC Transporters in Microorganisms Edited by Alicia Ponte-Sucre, Caister Academic Press. ISBN: 978-1-904455-49-3

Further reading: ABC Transporters as Targets against Drug Resistance

Labels: ABC proteins, ABC systems, ATP binding, ATP-binding cassette, efflux pumps, multidrug resistance, super-families