ABC transporters are fascinating molecular machines that use the energy of ATP to catalyze the transport of a tremendous variety of substrates across biological membranes in a vectorial fashion. All ABC transporters analyzed so far are composed of two nucleotide-binding domains (NBD) and two transmembrane domains (TMD) that can be arranged in any possible combination. However, additional transmembrane segments or extended NBDs, raise the possibility that these extensions act as platforms to interact with additional proteins with functional or regulatory consequences.

Recent crystal structures of isolated NBDs in different functional states and the structures of intact ABC transporters have elucidated the three-dimensional architecture, domain-domain interactions and putative signaling pathways in these membrane proteins that guarantee efficient substrate recognition and translocation in an ATP-dependent manner.

from Thorsten Jumpertz, I. Barry Holland and Lutz Schmitt (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: molecular machines, nucleotide-binding domains, translocation, two transmembrane domains